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

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

Index: tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate b/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
index 93da12737b89fb857bb4f42dff7ce764a8122475..1e4b2396e6d7f60ab1d554d120f6296c79536366 100644
--- a/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
+++ b/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
@@ -22,6 +22,13 @@ $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
     }
     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) {
@@ -57,6 +64,11 @@ $if DART2JS
           screenX, screenY, clientX, clientY, ctrlKey, altKey, shiftKey,
           metaKey, button, relatedTarget, axis);
     } else {
+$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,
@@ -76,6 +88,14 @@ $endif
 $!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)) {
@@ -83,7 +103,7 @@ $if DART2JS
       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
 
@@ -93,10 +113,10 @@ $if DART2JS
         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;
     }
@@ -104,6 +124,14 @@ $if DART2JS
         '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)) {
@@ -111,7 +139,7 @@ $if DART2JS
       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.
@@ -124,9 +152,9 @@ $if DART2JS
         // 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;
     }
@@ -193,9 +221,26 @@ $if DART2JS
       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
 }