MacViews: Support continuous scrolling and horizontal scrolling

ui/views/cocoa/bridged_content_view.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ui/views/cocoa/bridged_content_view.h"
 
 #include "base/logging.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #include "ui/base/ime/text_input_client.h"
@@ skipping 131 matching lines @@
 }
 
 - (void)mouseMoved:(NSEvent*)theEvent {
   // Note: mouseEntered: and mouseExited: are not handled separately.
   // |hostedView_| is responsible for converting the move events into entered
   // and exited events for the view heirarchy.
   [self handleMouseEvent:theEvent];
 }
 
 - (void)scrollWheel:(NSEvent*)theEvent {
-  [self handleMouseEvent:theEvent];
+  if (!hostedView_)
+    return;
+
+  ui::MouseWheelEvent event(theEvent);
+  hostedView_->GetWidget()->OnMouseEvent(&event);
 }
 
 - (void)deleteBackward:(id)sender {
   [self doCommandByID:IDS_DELETE_BACKWARD];
 }
 
 - (void)deleteForward:(id)sender {
   [self doCommandByID:IDS_DELETE_FORWARD];
 }
 
@@ skipping 148 matching lines @@
   }
 
   return [super accessibilityAttributeValue:attribute];
 }
 
 - (id)accessibilityHitTest:(NSPoint)point {
   return [hostedView_->GetNativeViewAccessible() accessibilityHitTest:point];
 }
 
 @end