Fix processing of mouse events on MacViews.

ui/events/cocoa/events_mac.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.
 
 #include "ui/events/event_utils.h"
 
 #include <Cocoa/Cocoa.h>
 #include <stdint.h>
 
 #include "base/logging.h"
@@ skipping 25 matching lines @@
     case NSRightMouseUp:
     case NSOtherMouseUp:
       return ET_MOUSE_RELEASED;
     case NSLeftMouseDragged:
     case NSRightMouseDragged:
     case NSOtherMouseDragged:
       return ET_MOUSE_DRAGGED;
     case NSMouseMoved:
       return ET_MOUSE_MOVED;
     case NSScrollWheel:
-      return ET_SCROLL;
+      return ET_MOUSEWHEEL;

[Avi (use Gerrit), 2016/10/25 15:34:50]

This was recently changed by Trent in r421082; why are you changing this back?

[snake, 2016/10/25 15:46:18]

views::Widget is not supported ET_SCROLL, only ET_MOUSEWHEEL.
see 
https://cs.chromium.org/chromium/src/ui/views/widget/widget.cc?rcl=0&l=1244
Alse see test, added in this CL: NativeWidgetMacTest.MouseWheelEvent
It is failed without this.

[snake, 2016/10/25 20:52:05]

Reverted. 

     case NSMouseEntered:
       return ET_MOUSE_ENTERED;
     case NSMouseExited:
       return ET_MOUSE_EXITED;
     case NSEventTypeSwipe:
       return ET_SCROLL_FLING_START;
     case NSAppKitDefined:
     case NSSystemDefined:
       return ET_UNKNOWN;
     case NSFlagsChanged:
@@ skipping 243 matching lines @@
   uint16_t return_value;
   [text getCharacters:&return_value];
   return return_value;
 }
 
 bool IsCharFromNative(const base::NativeEvent& native_event) {
   return false;
 }
 
 }  // namespace ui