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 5f621fc69fe992f920b7bf6a2782c94667d8eb2e..596fbf828dd754012b1025b403bd2d08f9e4322e 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -26888,6 +26888,10 @@ class WheelEvent extends MouseEvent {
       eventType = 'MouseScrollEvents';
     }
     final event = document.$dom_createEvent(eventType);
+    // Dartium always needs these flipped because we're essentially always
+    // polyfilling (see similar dart2js code as well)
+    deltaX = -deltaX;
+    deltaY = -deltaY;
       // Fallthrough for Dartium.
       event.$dom_initMouseEvent(type, canBubble, cancelable, view, detail,
           screenX, screenY, clientX, clientY, ctrlKey, altKey, shiftKey,
@@ -26932,10 +26936,27 @@ class WheelEvent extends MouseEvent {
   void $dom_initWebKitWheelEvent(int wheelDeltaX, int wheelDeltaY, Window view, int screenX, int screenY, int clientX, int clientY, bool ctrlKey, bool altKey, bool shiftKey, bool metaKey) native "WheelEvent_initWebKitWheelEvent_Callback";
 
 
+  /**
+   * The amount that is expected to scroll horizontally, in units determined by
+   * [deltaMode].
+   *
+   * See also:
+   *
+   * * [WheelEvent.deltaX](http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html#events-WheelEvent-deltaX) from the W3C.
+   */
   @DomName('WheelEvent.deltaX')
-  num get deltaX => $dom_wheelDeltaX;
+  num get deltaX => -$dom_wheelDeltaX;
+
+  /**
+   * The amount that is expected to scroll vertically, in units determined by
+   * [deltaMode].
+   *
+   * See also:
+   *
+   * * [WheelEvent.deltaY](http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html#events-WheelEvent-deltaY) from the W3C.
+   */
   @DomName('WheelEvent.deltaY')
-  num get deltaY => $dom_wheelDeltaY;
+  num get deltaY => -$dom_wheelDeltaY;
 }
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a