Allow "bulk editing" of the CssStyleDeclaration objects in an ElementList as well

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index 6bd9e6c6428990929562323e0eef3bbd4756ed95..6ccd84979608b179fd08a25c69014d497ca75bab 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -2634,7 +2634,8 @@ class CssRule extends Interceptor native "CSSRule" {
 
 
 @DomName('CSSStyleDeclaration')
-class CssStyleDeclaration extends Interceptor native "CSSStyleDeclaration,MSStyleCSSProperties,CSS2Properties" {
+ class CssStyleDeclaration  extends Interceptor with 
+    CssStyleDeclarationMixin  native "CSSStyleDeclaration,MSStyleCSSProperties,CSS2Properties" {
   factory CssStyleDeclaration() => new CssStyleDeclaration.css('');
 
   factory CssStyleDeclaration.css(String css) {
@@ -2642,7 +2643,43 @@ class CssStyleDeclaration extends Interceptor native "CSSStyleDeclaration,MSStyl
     style.cssText = css;
     return style;
   }
+}
+
+/**
+ * A collection of [CssStyleDeclaration]s that are associated with an
+ * [ElementList].
+ *
+ * Grouping the style objects all together provides easy editing of specific
+ * properties of a collection of elements. Setting a specific property value
+ * will set that property in all [Element]s in the [ElementList]. Getting a
+ * specific property value will return the value of the property of the first
+ * element in the [ElementList].
+ */
+class CssStyleDeclarationSet  extends Interceptor with CssStyleDeclarationMixin {
+  final Iterable<Element> _elementIterable;
+  Iterable<CssStyleDeclaration> _elementCssStyleDeclarationSetIterable;
+
+  CssStyleDeclarationSet._(this._elementIterable) {
+    _elementCssStyleDeclarationSetIterable = new List.from(
+        _elementIterable).map((e) => e.style);
+  }
 
+  String getPropertyValue(String propertyName) =>
+      _elementCssStyleDeclarationSetIterable.first.getPropertyValue(
+          propertyName);
+
+  void setProperty(String propertyName, String value, [String priority]) {
+    _elementCssStyleDeclarationSetIterable.forEach((e) =>
+        e.setProperty(propertyName, value, priority));
+  }
+  // Important note: CssStyleDeclarationSet does NOT implement every method
+  // available in CssStyleDeclaration. Some of the methods don't make so much
+  // sense in terms of having a resonable value to return when you're
+  // considering a list of Elements. You will need to manually add any of the
+  // items in the MEMBERS set if you want that functionality.
+}
+
+abstract class CssStyleDeclarationMixin {
 
   @DomName('CSSStyleDeclaration.cssText')
   @DocsEditable()
@@ -2677,7 +2714,6 @@ class CssStyleDeclaration extends Interceptor native "CSSStyleDeclaration,MSStyl
   @DocsEditable()
   String removeProperty(String propertyName) native;
 
-
   String getPropertyValue(String propertyName) {
     var propValue = _getPropertyValue(propertyName);
     return propValue != null ? propValue : '';
@@ -7989,6 +8025,9 @@ abstract class ElementList<T extends Element> extends ListBase<T> {
   /** Replace the classes with `value` for every element in this list. */
   set classes(Iterable<String> value);
 
+  /** The union of all styles associated with the [Element]s in this list. */
+  CssStyleDeclarationSet get style;
+
   /** 
    * Access dimensions and position of the Elements in this list.
    * 
@@ -8084,6 +8123,9 @@ class _FrozenElementList<T extends Element> extends ListBase<T> implements Eleme
 
   CssClassSet get classes => new _MultiElementCssClassSet(_elementList);
 
+  CssStyleDeclarationSet get style => 
+      new CssStyleDeclarationSet._(_elementList);
+
   void set classes(Iterable<String> value) {
     _elementList.forEach((e) => e.classes = value);
   }