Changing window.requestLayoutFrame into a microtask API

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 b554609c25a574d0d8b2ca83d67ff216d9dd1d45..8140a79a3dca4c7a8cd319aa714a4447b9b69692 100644
--- a/tools/dom/templates/html/impl/impl_Element.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Element.darttemplate
@@ -707,27 +707,20 @@ $(ANNOTATIONS)abstract class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
    * [style] property, which contains only the values specified directly on this
    * element.
    *
-   * See also:
-   *
-   * * [CSS Inheritance and Cascade](http://docs.webplatform.org/wiki/tutorials/inheritance_and_cascade)
-   */
-  Future<CssStyleDeclaration> get computedStyle {
-     // TODO(jacobr): last param should be null, see b/5045788
-     return getComputedStyle('');
-  }
-
-  /**
-   * Returns the computed styles for pseudo-elements such as `::after`,
-   * `::before`, `::marker`, `::line-marker`.
+   * PseudoElement can be values such as `::after`, `::before`, `::marker`,
+   * `::line-marker`.
    *
    * See also:
    *
+   * * [CSS Inheritance and Cascade](http://docs.webplatform.org/wiki/tutorials/inheritance_and_cascade)
    * * [Pseudo-elements](http://docs.webplatform.org/wiki/css/selectors/pseudo-elements)
    */
-  Future<CssStyleDeclaration> getComputedStyle(String pseudoElement) {
-    return _createMeasurementFuture(
-        () => window.$dom_getComputedStyle(this, pseudoElement),
-        new Completer<CssStyleDeclaration>());
+  CssStyleDeclaration getComputedStyle([String pseudoElement]) {
+    if (pseudoElement == null) {
+      pseudoElement = '';
+    }
+    // TODO(jacobr): last param should be null, see b/5045788
+    return window.$dom_getComputedStyle(this, pseudoElement);
   }
 
   /**