fix(web platform): Do not barf on attribute selectors.

See #1189

lib/core_dom/web_platform.dart

@@ -35,11 +35,17 @@ class WebPlatform {
 
   void shimShadowDom(dom.Element root, String selector) {
     if (shadowDomShimRequired) {
-
       // This adds an empty attribute with the name of the component tag onto
       // each element in the shadow root.
-      root.querySelectorAll("*")
-          .forEach((n) => n.attributes[selector] = "");
+      //
+      // Remove the try-catch once https://github.com/angular/angular.dart/issues/1189 is
+      // fixed.
+      try {
+        root.querySelectorAll("*")
+        .forEach((n) => n.attributes[selector] = "");
+      } catch (e, s) {
+        print("WARNING: Failed to set up Shadow DOM shim for $selector.\n$e\n$s");
+      }
     }
   }
 }

test/core_dom/web_platform_spec.dart

@@ -10,6 +10,7 @@ main() {
     beforeEachModule((Module module) {
       module
         ..bind(WebPlatformTestComponent)
+        ..bind(WebPlatformTestComponentWithAttribute)
         ..bind(InnerComponent)
         ..bind(OuterComponent)
         ..bind(WebPlatform, toValue: new WebPlatform());
@@ -54,6 +55,24 @@ main() {
       }
     }));
 
+    it('should not crash with an attribute selector; but wont work either..',
+       async((TestBed _, MockHttpBackend backend, WebPlatform platform) {
+
+      backend
+        ..expectGET('style.css').respond(200, 'span { background-color: red; '
+      '}')
+        ..expectGET('template.html').respond(200, '<span>foo</span>');
+
+      Element element = e('<span><test-wptca a><span>ignore'
+      '</span></test-wptca></span>');
+
+      _.compile(element);
+
+      microLeap();
+      backend.flush();
+      microLeap();
+    }));
+
     it('should scope :host styles to the primary element.',
     async((TestBed _, MockHttpBackend backend, WebPlatform platform) {
 
@@ -176,6 +195,14 @@ main() {
 class WebPlatformTestComponent {
 }
 
+@Component(
+    selector: "test-wptca[a]",
+    publishAs: "ctrl",
+    templateUrl: "template.html",
+    cssUrl: "style.css")
+class WebPlatformTestComponentWithAttribute {
+}
+
 @Component(
     selector: "my-inner",
     publishAs: "ctrl",