Implement measurement using futures

client/html/src/Document.dart

Index: client/html/src/Document.dart
diff --git a/client/html/src/Document.dart b/client/html/src/Document.dart
index f6cf9bf8893ab19b3e534b5ddd01b2404ce97c83..a397393ee9be549de8587b50948da0cae19ff5e9 100644
--- a/client/html/src/Document.dart
+++ b/client/html/src/Document.dart
@@ -43,7 +43,7 @@ interface Document extends Element /*, common.NodeSelector */ {
 
   String get lastModified();
 
-  // TODO(jacobr): remove once on.contentLoaded is changed to return a Promise.
+  // TODO(jacobr): remove once on.contentLoaded is changed to return a Future.
   String get readyState();
 
   String get referrer();
@@ -59,12 +59,12 @@ interface Document extends Element /*, common.NodeSelector */ {
 
   String get webkitVisibilityState();
 
-  Promise<Range> caretRangeFromPoint([int x, int y]);
+  Future<Range> caretRangeFromPoint([int x, int y]);
 
   // TODO(jacobr): remove.
   Element createElement([String tagName]);
 
-  Promise<Element> elementFromPoint([int x, int y]);
+  Future<Element> elementFromPoint([int x, int y]);
 
   bool execCommand([String command, bool userInterface, String value]);
 
@@ -87,4 +87,6 @@ interface Document extends Element /*, common.NodeSelector */ {
   void set manifest(String value);
 
   DocumentEvents get on();
+
+  Future<ElementRect> get rect();
 }