Re-try of Flipping the direction of WheelEvent.deltaX/Y to follow standards

tools/dom/templates/html/impl/impl_WheelEvent.darttemplate

 // 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
 // BSD-style license that can be found in the LICENSE file.
 
 part of $LIBRARYNAME;
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
   factory WheelEvent(String type,
       {Window view, int deltaX: 0, int deltaY: 0,
       int detail: 0, int screenX: 0, int screenY: 0, int clientX: 0,
       int clientY: 0, int button: 0, bool canBubble: true,
       bool cancelable: true, bool ctrlKey: false, bool altKey: false,
       bool shiftKey: false, bool metaKey: false, EventTarget relatedTarget}) {
 
     if (view == null) {
       view = window;
     }
     var eventType = 'WheelEvent';
     if (Device.isFirefox) {
       eventType = 'MouseScrollEvents';
     }
     final event = document.$dom_createEvent(eventType);
 $if DART2JS
+    // If polyfilling, then flip these because we'll flip them back to match
+    // the W3C standard:
+    // http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html#events-WheelEvent-deltaY
+    if (JS('bool', '#.deltaY === undefined', event)) {
+      deltaX = -deltaX;
+      deltaY = -deltaY;
+    }
     if (event._hasInitWheelEvent) {
       var modifiers = [];
       if (ctrlKey) {
         modifiers.push('Control');
       }
       if (altKey) {
         modifiers.push('Alt');
       }
       if (shiftKey) {
         modifiers.push('Shift');
@@ skipping 15 matching lines @@
         detail = deltaY;
         axis = JS('int', 'MouseScrollEvent.VERTICAL_AXIS');
       } else if (deltaX != 0) {
         detail = deltaX;
         axis = JS('int', 'MouseScrollEvent.HORIZONTAL_AXIS');
       }
       event._initMouseScrollEvent(type, canBubble, cancelable, view, detail,
           screenX, screenY, clientX, clientY, ctrlKey, altKey, shiftKey,
           metaKey, button, relatedTarget, axis);
     } else {
+$else
+    // Dartium always needs these flipped because we're essentially always
+    // polyfilling (see similar dart2js code as well)
+    deltaX = -deltaX;
+    deltaY = -deltaY;
 $endif
       // Fallthrough for Dartium.
       event.$dom_initMouseEvent(type, canBubble, cancelable, view, detail,
           screenX, screenY, clientX, clientY, ctrlKey, altKey, shiftKey,
           metaKey, button, relatedTarget);
       event.$dom_initWebKitWheelEvent(deltaX,
           deltaY ~/ 120, // Chrome does an auto-convert to pixels.
           view, screenX, screenY, clientX, clientY, ctrlKey, altKey, shiftKey,
           metaKey);
 $if DART2JS
     }
 $endif
 
     return event;
   }
 
 $!MEMBERS
 
 $if DART2JS
+  /**
+   * 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 {
     if (JS('bool', '#.deltaY !== undefined', this)) {
       // W3C WheelEvent
       return this._deltaY;
     } else if (JS('bool', '#.wheelDelta !== undefined', this)) {
       // Chrome and IE
-      return this._wheelDelta;
+      return -this._wheelDelta;
     } else if (JS('bool', '#.detail !== undefined', this)) {
       // Firefox
 
       // Handle DOMMouseScroll case where it uses detail and the axis to
       // differentiate.
       if (JS('bool', '#.axis == MouseScrollEvent.VERTICAL_AXIS', this)) {
         var detail = this._detail;
         // Firefox is normally the number of lines to scale (normally 3)
         // so multiply it by 40 to get pixels to move, matching IE & WebKit.
-        if (detail < 100) {
-          return detail * 40;
+        if (detail.abs() < 100) {
+          return -detail * 40;
         }
-        return detail;
+        return -detail;
       }
       return 0;
     }
     throw new UnsupportedError(
         'deltaY is not supported');
   }
 
+  /**
+   * 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 {
     if (JS('bool', '#.deltaX !== undefined', this)) {
       // W3C WheelEvent
       return this._deltaX;
     } else if (JS('bool', '#.wheelDeltaX !== undefined', this)) {
       // Chrome
-      return this._wheelDeltaX;
+      return -this._wheelDeltaX;
     } else if (JS('bool', '#.detail !== undefined', this)) {
       // Firefox and IE.
       // IE will have detail set but will not set axis.
 
       // Handle DOMMouseScroll case where it uses detail and the axis to
       // differentiate.
       if (JS('bool', '#.axis !== undefined && '
         '#.axis == MouseScrollEvent.HORIZONTAL_AXIS', this, this)) {
         var detail = this._detail;
         // Firefox is normally the number of lines to scale (normally 3)
         // so multiply it by 40 to get pixels to move, matching IE & WebKit.
         if (detail < 100) {
-          return detail * 40;
+          return -detail * 40;
         }
-        return detail;
+        return -detail;
       }
       return 0;
     }
     throw new UnsupportedError(
         'deltaX is not supported');
   }
 
   @DomName('WheelEvent.deltaMode')
   int get deltaMode {
     if (JS('bool', '!!(#.deltaMode)', this)) {
@@ skipping 46 matching lines @@
       int clientY,
       int button,
       EventTarget relatedTarget,
       String modifiersList,
       int deltaX,
       int deltaY,
       int deltaZ,
       int deltaMode) native;
 
 $else
+  /**
+   * 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;
 $endif
 }