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..502ac9c36415573f2967cecc907d6ab00b8556ae 100644
--- a/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
+++ b/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
@@ -22,6 +22,11 @@ $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
     }
     final event = document.$dom_createEvent(eventType);
 $if DART2JS
+    // If polyfilling, then flip these to match W3C wheel spec.

[Emily Fortuna, 2013/04/02 23:59:09]

Can you link to the w3c spec or (better) say which direction is positive
according to the spec here?

[blois, 2013/04/03 00:35:34]

Added link to the spec, but it doesn't actually specify which direction is
positive. Primary thing is that if we're flipping the values on the read-back,
then we should unflip them here so manually generated events are consistent.

IE10 and FF recently added support for the W3C events (though IE does not
publicize it properly, so we don't use it there). I was able to validate that
they are both consistent in their direction, so this adjusts the polyfills to be
consistent as well.

+    if (JS('bool', '#.deltaY === undefined', event)) {
+      deltaX = -deltaX;
+      deltaY = -deltaY;
+    }
     if (event._hasInitWheelEvent) {
       var modifiers = [];
       if (ctrlKey) {
@@ -83,7 +88,7 @@ $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
 
@@ -94,9 +99,9 @@ $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;
     }
@@ -111,7 +116,7 @@ $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 +129,9 @@ $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;
     }
@@ -194,8 +199,8 @@ $if DART2JS
 
 $else
   @DomName('WheelEvent.deltaX')
-  num get deltaX => $dom_wheelDeltaX;
+  num get deltaX => -$dom_wheelDeltaX;
   @DomName('WheelEvent.deltaY')
-  num get deltaY => $dom_wheelDeltaY;
+  num get deltaY => -$dom_wheelDeltaY;
 $endif
 }