From 298457610b957199088468ac0a58572e967bb7b4 Mon Sep 17 00:00:00 2001
From: Russell Bicknell <bicknellr@google.com>
Date: Tue, 15 Dec 2015 17:47:15 -0800
Subject: [PATCH] DOM API implementation of `activeElement`.

---
 bower.json                          |   2 +-
 src/lib/dom-api-shadow.html         |   7 +
 src/lib/dom-api-shady.html          |  43 ++++-
 test/unit/polymer-dom-elements.html | 242 +++++++++++++++++++++++
 test/unit/polymer-dom-shadow.html   |   4 +
 test/unit/polymer-dom.html          |   4 +
 test/unit/polymer-dom.js            | 288 ++++++++++++++++++++++++++++
 7 files changed, 588 insertions(+), 2 deletions(-)

diff --git a/bower.json b/bower.json
index b6655cda87..a13c6ad749 100644
--- a/bower.json
+++ b/bower.json
@@ -20,7 +20,7 @@
     "url": "https://github.com/Polymer/polymer.git"
   },
   "dependencies": {
-    "webcomponentsjs": "^0.7.18"
+    "webcomponentsjs": "^0.7.20"
   },
   "devDependencies": {
     "web-component-tester": "*"
diff --git a/src/lib/dom-api-shadow.html b/src/lib/dom-api-shadow.html
index cc73842b6f..3cdb7ea8fd 100644
--- a/src/lib/dom-api-shadow.html
+++ b/src/lib/dom-api-shadow.html
@@ -58,6 +58,13 @@
 
   Object.defineProperties(DomApi.prototype, {
 
+    activeElement: {
+      get: function() {
+        return Polymer.DomApi.wrap(this.node).activeElement;
+      },
+      configurable: true
+    },
+    
     childNodes: {
       get: function() {
         return TreeApi.arrayCopyChildNodes(this.node);
diff --git a/src/lib/dom-api-shady.html b/src/lib/dom-api-shady.html
index 64e41c1c49..9d00661e95 100644
--- a/src/lib/dom-api-shady.html
+++ b/src/lib/dom-api-shady.html
@@ -422,6 +422,47 @@
 
   Object.defineProperties(DomApi.prototype, {
 
+    activeElement: {
+      get: function() {
+        var active = document.activeElement;
+        if (!active) {
+          return null;
+        }
+        var isShadyRoot = !!this.node._isShadyRoot;
+        if (this.node !== document) {
+          // If this node isn't a document or shady root, then it doesn't
+          // have an active element.
+          if (!isShadyRoot) {
+            return null;
+          }
+          // If this shady root's host is the active element or the active
+          // element is not a descendant of the host, then it doesn't have
+          // an active element.
+          if (this.node.host === active ||
+              !this.node.host.contains(active)) {
+            return null;
+          }
+          // If the active element is a light descendant of the shady root's
+          // host, return the active element.
+          if (this.node.host !== active &&
+              this._contains(this.node.host, active)) {
+            return active;
+          }
+        }
+        // This node is either the document or a shady root of which the
+        // active element is a descendant of its host; iterate upwards to
+        // find the active element's most shallow host.
+        var activeRoot = Polymer.dom(active).getOwnerRoot();
+        while (activeRoot && activeRoot !== this.node &&
+            !(isShadyRoot && this._contains(this.node.host, active))) {
+          active = activeRoot.host;
+          activeRoot = Polymer.dom(active).getOwnerRoot();
+        }
+        return active;
+      },
+      configurable: true
+    },
+
     childNodes: {
       get: function() {
         var c$ = TreeApi.Logical.getChildNodes(this.node);
@@ -569,4 +610,4 @@
   };
 
 })();
-</script>
\ No newline at end of file
+</script>
diff --git a/test/unit/polymer-dom-elements.html b/test/unit/polymer-dom-elements.html
index c0b28546aa..a4c39fd7a1 100644
--- a/test/unit/polymer-dom-elements.html
+++ b/test/unit/polymer-dom-elements.html
@@ -357,3 +357,245 @@
   });
   </script>
 </dom-module>
+
+
+<dom-module id="x-shadow-host-root">
+  <template>
+    <content></content>
+    <div>
+      <div>
+        <x-shadow-host-root-0>
+          <x-shadow-host-root-0-light></x-shadow-host-root-0-light>
+        </x-shadow-host-root-0>
+      </div>
+    </div>
+    <div>
+      <x-shadow-host-root-1>
+        <x-shadow-host-root-1-light></x-shadow-host-root-1-light>
+      </x-shadow-host-root-1>
+    </div>
+  </template>
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-light">
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-light',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-0">
+  <template>
+    <content></content>
+    <div>
+      <x-shadow-host-root-0-0>
+        <x-shadow-host-root-0-0-light></x-shadow-host-root-0-0-light>
+      </x-shadow-host-root-0-0>
+    </div>
+    <x-shadow-host-root-0-1>
+      <x-shadow-host-root-0-1-light></x-shadow-host-root-0-1-light>
+    </x-shadow-host-root-0-1>
+  </template>
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-0',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-0-light">
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-0-light',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-0-0">
+  <template>
+    <content></content>
+  </template>
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-0-0',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-0-0-light">
+  <template>
+    <div>
+      <div>
+        <x-shadow-host-root-0-0-light-0></x-shadow-host-root-0-0-light-0>
+      </div>
+    </div>
+  </template>
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-0-0-light',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-0-0-light-0">
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-0-0-light-0',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-0-1">
+  <template>
+    <content></content>
+  </template>
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-0-1',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-0-1-light">
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-0-1-light',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-1">
+  <template>
+    <content></content>
+    <div>
+      <x-shadow-host-root-1-0>
+        <x-shadow-host-root-1-0-light></x-shadow-host-root-1-0-light>
+      </x-shadow-host-root-1-0>
+    </div>
+    <div>
+      <div>
+        <div>
+          <x-shadow-host-root-1-1>
+            <x-shadow-host-root-1-1-light></x-shadow-host-root-1-1-light>
+          </x-shadow-host-root-1-1>
+        </div>
+      </div>
+    </div>
+  </template>
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-1',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-1-light">
+  <template>
+    <x-shadow-host-root-1-light-0></x-shadow-host-root-1-light-0>
+  </template>
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-1-light',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-1-light-0">
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-1-light-0',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-1-0">
+  <template>
+    <content></content>
+  </template>
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-1-0',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-1-0-light">
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-1-0-light',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-1-1">
+  <template>
+    <content></content>
+  </template>
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-1-1',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
+
+<dom-module id="x-shadow-host-root-1-1-light">
+  <script>
+    Polymer({
+      is: 'x-shadow-host-root-1-1-light',
+      hostAttributes: {
+        tabindex: '-1'
+      }
+    });
+  </script>
+</dom-module>
diff --git a/test/unit/polymer-dom-shadow.html b/test/unit/polymer-dom-shadow.html
index f1f5267810..cc2a5c2c81 100644
--- a/test/unit/polymer-dom-shadow.html
+++ b/test/unit/polymer-dom-shadow.html
@@ -57,6 +57,10 @@
 
 <x-wrapped></x-wrapped>
 
+<x-shadow-host-root>
+  <x-shadow-host-root-light></x-shadow-host-root-light>
+</x-shadow-host-root>
+
 <script src="polymer-dom.js"></script>
 
 </body>
diff --git a/test/unit/polymer-dom.html b/test/unit/polymer-dom.html
index 7899b1c2df..7f0e15c52e 100644
--- a/test/unit/polymer-dom.html
+++ b/test/unit/polymer-dom.html
@@ -57,6 +57,10 @@
 
 <x-wrapped></x-wrapped>
 
+<x-shadow-host-root>
+  <x-shadow-host-root-light></x-shadow-host-root-light>
+</x-shadow-host-root>
+
 <script src="polymer-dom.js"></script>
 
 </body>
diff --git a/test/unit/polymer-dom.js b/test/unit/polymer-dom.js
index c11a6e8dd5..f6e06747ea 100644
--- a/test/unit/polymer-dom.js
+++ b/test/unit/polymer-dom.js
@@ -802,6 +802,294 @@ suite('Polymer.dom accessors', function() {
     assert.equal(testElement.children.length, 3);
   });
 
+  suite('Polymer.dom activeElement', function() {
+    var r;
+      // light
+        var r_l
+      // shadow
+        var r_0;
+          // light
+            var r_0_l;
+          // shadow
+            var r_0_0;
+              // light
+                var r_0_0_l;
+                  // shadow
+                    var r_0_0_l_0;
+            var r_0_1;
+              // light
+                var r_0_1_l;
+        var r_1;
+          // light
+            var r_1_l;
+              // shadow
+                var r_1_l_0;
+          // shadow
+            var r_1_0;
+              // light
+                var r_1_0_l;
+            var r_1_1;
+              // light
+                var r_1_1_l;
+
+    suiteSetup(function() {
+      r = Polymer.dom(document).querySelector('x-shadow-host-root');
+        r_l = Polymer.dom(r).querySelector('x-shadow-host-root-light');
+        r_0 = Polymer.dom(r.root).querySelector('x-shadow-host-root-0');
+          r_0_l = Polymer.dom(r_0).querySelector('x-shadow-host-root-0-light');
+          r_0_0 = Polymer.dom(r_0.root).querySelector('x-shadow-host-root-0-0');
+            r_0_0_l = Polymer.dom(r_0_0).querySelector('x-shadow-host-root-0-0-light');
+              r_0_0_l_0 = Polymer.dom(r_0_0_l.root).querySelector('x-shadow-host-root-0-0-light-0');
+          r_0_1 = Polymer.dom(r_0.root).querySelector('x-shadow-host-root-0-1');
+            r_0_1_l = Polymer.dom(r_0_1).querySelector('x-shadow-host-root-0-1-light');
+        r_1 = Polymer.dom(r.root).querySelector('x-shadow-host-root-1');
+          r_1_l = Polymer.dom(r_1).querySelector('x-shadow-host-root-1-light');
+            r_1_l_0 = Polymer.dom(r_1_l.root).querySelector('x-shadow-host-root-1-light-0');
+          r_1_0 = Polymer.dom(r_1.root).querySelector('x-shadow-host-root-1-0');
+            r_1_0_l = Polymer.dom(r_1_0).querySelector('x-shadow-host-root-1-0-light');
+          r_1_1 = Polymer.dom(r_1.root).querySelector('x-shadow-host-root-1-1');
+            r_1_1_l = Polymer.dom(r_1_1).querySelector('x-shadow-host-root-1-1-light');
+    });
+
+    test('r.focus()', function() {
+      r.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, null, 'r.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_l.focus()', function() {
+      r_l.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r_l, 'document.activeElement === r_l');
+      assert.equal(Polymer.dom(r.root).activeElement, r_l, 'r.root.activeElement === r_l');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_0.focus()', function() {
+      r_0.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_0, 'r.root.activeElement === r_0');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_0_l.focus()', function() {
+      r_0_l.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_0_l, 'r.root.activeElement === r_0_l');
+      assert.equal(Polymer.dom(r_0.root).activeElement, r_0_l, 'r_0.root.activeElement === r_0_l');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_0_0.focus()', function() {
+      r_0_0.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_0, 'r.root.activeElement === r_0');
+      assert.equal(Polymer.dom(r_0.root).activeElement, r_0_0, 'r_0.root.activeElement === r_0_0');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_0_0_l.focus()', function() {
+      r_0_0_l.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_0, 'r.root.activeElement === r_0');
+      assert.equal(Polymer.dom(r_0.root).activeElement, r_0_0_l, 'r_0.root.activeElement === r_0_0_l');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, r_0_0_l, 'r_0_0.root.activeElement === r_0_0_l');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_0_0_l_0.focus()', function() {
+      r_0_0_l_0.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_0, 'r.root.activeElement === r_0');
+      assert.equal(Polymer.dom(r_0.root).activeElement, r_0_0_l, 'r_0.root.activeElement === r_0_0_l');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, r_0_0_l, 'r_0_0.root.activeElement === r_0_0_l');
+      assert.equal(Polymer.dom(r_0_0_l.root).activeElement, r_0_0_l_0, 'r_0_0_l.root.activeElement === r_0_0_l_0');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_0_1.focus()', function() {
+      r_0_1.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_0, 'r.root.activeElement === r_0');
+      assert.equal(Polymer.dom(r_0.root).activeElement, r_0_1, 'r_0.root.activeElement === r_0_1');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_0_1_l.focus()', function() {
+      r_0_1_l.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_0, 'r.root.activeElement === r_0');
+      assert.equal(Polymer.dom(r_0.root).activeElement, r_0_1_l, 'r_0.root.activeElement === r_0_1_l');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, r_0_1_l, 'r_0_1.root.activeElement === r_0_1_l');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_1.focus()', function() {
+      r_1.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_1, 'r.root.activeElement === r_1');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, null, 'r_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_1_l.focus()', function() {
+      r_1_l.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_1_l, 'r.root.activeElement === r_1_l');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, r_1_l, 'r_1.root.activeElement === r_1_l');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_1_l_0.focus()', function() {
+      r_1_l_0.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_1_l, 'r.root.activeElement === r_1_l');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, r_1_l, 'r_1.root.activeElement === r_1_l');
+      assert.equal(Polymer.dom(r_1_l.root).activeElement, r_1_l_0, 'r_1.root.activeElement === r_1_l_0');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_1_0.focus()', function() {
+      r_1_0.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_1, 'r.root.activeElement === r_1');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, r_1_0, 'r_1.root.activeElement === r_1_0');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_1_0_l.focus()', function() {
+      r_1_0_l.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_1, 'r.root.activeElement === r_1');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, r_1_0_l, 'r_1.root.activeElement === r_1_0_l');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, r_1_0_l, 'r_1_0.root.activeElement === r_1_0_l');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_1_1.focus()', function() {
+      r_1_1.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_1, 'r.root.activeElement === r_1');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, r_1_1, 'r_1.root.activeElement === r_1_1');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('r_1_1_l.focus()', function() {
+      r_1_1_l.focus();
+
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_1, 'r.root.activeElement === r_1');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, r_1_1_l, 'r_1.root.activeElement === r_1_1_l');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, r_1_1_l, 'r_1_1.root.activeElement === r_1_1_l');
+    });
+
+    test('setting activeElement on document has no effect', function() {
+      r_1_1.focus();
+
+      Polymer.dom(document).activeElement = "abc";
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_1, 'r.root.activeElement === r_1');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, r_1_1, 'r_1.root.activeElement === r_1_1');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+
+    test('setting activeElement on a shadow root has no effect', function() {
+      r_1_1.focus();
+
+      Polymer.dom(r_1.root).activeElement = "abc";
+      assert.equal(Polymer.dom(document).activeElement, r, 'document.activeElement === r');
+      assert.equal(Polymer.dom(r.root).activeElement, r_1, 'r.root.activeElement === r_1');
+      assert.equal(Polymer.dom(r_0.root).activeElement, null, 'r_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_0.root).activeElement, null, 'r_0_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_0_1.root).activeElement, null, 'r_0_1.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1.root).activeElement, r_1_1, 'r_1.root.activeElement === r_1_1');
+      assert.equal(Polymer.dom(r_1_0.root).activeElement, null, 'r_1_0.root.activeElement === null');
+      assert.equal(Polymer.dom(r_1_1.root).activeElement, null, 'r_1_1.root.activeElement === null');
+    });
+  });
 });
 
 suite('Polymer.dom non-distributed elements', function() {