Revert the revert.

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index fa386099db49e33b43ecba569c04efd6fa29fbdd..e1424ad95943e37b21fdcefa22297da2c4db64b1 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -14012,6 +14012,17 @@ class HttpRequest extends EventTarget {
   }
 
   /**
+   * Checks to see if the current platform supports making cross origin
+   * requests.
+   *
+   * Note that even if cross origin requests are supported, they still may fail
+   * if the destination server does not support CORS requests.
+   */
+  static bool get supportsCrossOrigin {
+    return true;
+  }
+
+  /**
    * Checks to see if the LoadEnd event is supported on the current platform.
    */
   static bool get supportsLoadEndEvent {