Merge pull request #1992 from Polymer/1786-kschaaf-domif-comments

Ensure style exists. Fixes #1786.

src/lib/template/dom-if.html

@@ -151,7 +151,9 @@
         var c$ = this._instance._children;
         for (var i=0; i<c$.length; i++) {
           var c = c$[i];
-          c.style.display = hidden ? 'none' : '';
+          if (c.style) {
+            c.style.display = hidden ? 'none' : '';
+          }
           c._hideTemplateChildren = hidden;
         }
       }

test/unit/dom-if-elements.html

@@ -34,16 +34,19 @@
 <dom-module id="x-nested-if">
   <template>
     <template is="dom-if" id="if-1" if="{{shouldStamp}}" on-dom-change="domUpdateHandler">
+      <!-- Comments should be good -->
       <x-foo on-test1="testHandler1"
              prop="{{prop}}"
              item-prop="{{item.prop}}">
       </x-foo>
       <template is="dom-if" id="if-2" if="{{shouldStamp}}">
+        <!-- Comments should be good -->
         <x-foo on-test2="testHandler2"
                prop="{{prop}}"
                item-prop="{{item.prop}}">
         </x-foo>
         <template is="dom-if" id="if-3" if="{{shouldStamp}}">
+        <!-- Comments should be good -->
           <x-foo on-test3="testHandler3"
                  prop="{{prop}}"
                  item-prop="{{item.prop}}">
@@ -81,14 +84,17 @@
 <dom-module id="x-nested-if-configured">
   <template>
     <template is="dom-if" id="if-1" if="{{shouldStamp}}">
+      <!-- Comments should be good -->
       <x-foo prop="{{prop}}"
              item-prop="{{item.prop}}">
       </x-foo>
       <template is="dom-if" id="if-2" if="{{shouldStamp}}">
+        <!-- Comments should be good -->
         <x-foo prop="{{prop}}"
                item-prop="{{item.prop}}">
         </x-foo>
         <template is="dom-if" id="if-3" if="{{shouldStamp}}">
+          <!-- Comments should be good -->
           <x-foo prop="{{prop}}"
                  item-prop="{{item.prop}}">
           </x-foo>