Cleaning up event constructors

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 e842da76f51f777e892a866573ffe328ef9bb1e8..a49a9792c068dd87a63411b98b85a11f389a9818 100644
--- a/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
+++ b/tools/dom/templates/html/impl/impl_WheelEvent.darttemplate
@@ -6,13 +6,16 @@ part of html;
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
-  factory WheelEvent(String type, Window view, int wheelDeltaX, int wheelDeltaY,
-      int detail, int screenX, int screenY, int clientX, int clientY,
-      int button,
-      [bool canBubble = true, bool cancelable = true, bool ctrlKey = false,
-      bool altKey = false, bool shiftKey = false, bool metaKey = false,
-      EventTarget relatedTarget = null]) {
-
+  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';
@@ -35,19 +38,19 @@ $if DART2JS
       }
       event._initWheelEvent(type, canBubble, cancelable, view, detail, screenX,
           screenY, clientX, clientY, button, relatedTarget, modifiers.join(' '),
-          wheelDeltaX, wheelDeltaY, 0, 0);
+          deltaX, deltaY, 0, 0);
     } else if (event._hasInitMouseScrollEvent) {
       var axis = 0;
       var detail = 0;
-      if (wheelDeltaX != 0 && wheelDeltaY != 0) {
+      if (deltaX != 0 && deltaY != 0) {
         throw UnsupportedError(
-            'Cannot modify wheelDeltaX and wheelDeltaY simultaneously');
+            'Cannot modify deltaX and deltaY simultaneously');
       }
-      if (wheelDeltaY != 0) {
-        detail = wheelDeltaY;
+      if (deltaY != 0) {
+        detail = deltaY;
         axis = JS('int', 'MouseScrollEvent.VERTICAL_AXIS');
-      } else if (wheelDeltaX != 0) {
-        detail = wheelDeltaX;
+      } else if (deltaX != 0) {
+        detail = deltaX;
         axis = JS('int', 'MouseScrollEvent.HORIZONTAL_AXIS');
       }
       event._initMouseScrollEvent(type, canBubble, cancelable, view, detail,
@@ -59,8 +62,8 @@ $endif
       event.$dom_initMouseEvent(type, canBubble, cancelable, view, detail,
           screenX, screenY, clientX, clientY, ctrlKey, altKey, shiftKey,
           metaKey, button, relatedTarget);
-      event.$dom_initWebKitWheelEvent(wheelDeltaX,
-          wheelDeltaY ~/ 120, // Chrome does an auto-convert to pixels.
+      event.$dom_initWebKitWheelEvent(deltaX,
+          deltaY ~/ 120, // Chrome does an auto-convert to pixels.
           view, screenX, screenY, clientX, clientY, ctrlKey, altKey, shiftKey,
           metaKey);
 $if DART2JS