Revert "Adding polyfill support for custom elements."

tools/dom/templates/html/impl/impl_Element.darttemplate

Index: tools/dom/templates/html/impl/impl_Element.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Element.darttemplate b/tools/dom/templates/html/impl/impl_Element.darttemplate
index 054c5e0eab520cda0e797214f581fa2bbd5581e5..cbea8c1aed4623ebbe6782df2bbf15f8827e0620 100644
--- a/tools/dom/templates/html/impl/impl_Element.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Element.darttemplate
@@ -244,7 +244,7 @@ abstract class ElementList<T extends Element> extends ListBase<T> {
    */
   @Experimental()
   CssRect get marginEdge;
-$!STREAM_GETTER_SIGNATURES
+$!STREAM_GETTER_SIGNATURES 
 }
 
 // TODO(jacobr): this is an inefficient implementation but it is hard to see
@@ -1170,20 +1170,6 @@ $endif
     Point p = Element._offsetToHelper(parentOffset, parent);
     return new Point(p.x + current.offsetLeft, p.y + current.offsetTop);
   }
-
-$if DART2JS
-  @JSName('innerHTML')
-  @DomName('HTMLElement.innerHTML')
-  String get innerHtml;
-
-  void set innerHtml(String value) {
-    JS('', '#.innerHTML = #', this, value);
-    // Polyfill relies on mutation observers for upgrading, but we want it
-    // immediate.
-    Platform.upgradeCustomElements(this);
-  }
-$endif
-
 $!MEMBERS
 }