[Ozone] Fix DCHECK and check for scroll events as well

ui/events/ozone/events_ozone.cc

 // Copyright (c) 2013 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/ozone/events_ozone.h"
 
 #include "ui/events/event.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/event_utils.h"
 
@@ skipping 26 matching lines @@
 }
 
 gfx::Point EventLocationFromNative(const base::NativeEvent& native_event) {
   return EventSystemLocationFromNative(native_event);
 }
 
 int GetChangedMouseButtonFlagsFromNative(
     const base::NativeEvent& native_event) {
   const ui::MouseEvent* event =
       static_cast<const ui::MouseEvent*>(native_event);
-  DCHECK(event->IsMouseEvent());
+  DCHECK(event->IsMouseEvent() || event->IsScrollEvent());
   return event->changed_button_flags();
 }
 
 KeyboardCode KeyboardCodeFromNative(const base::NativeEvent& native_event) {
   const ui::KeyEvent* event = static_cast<const ui::KeyEvent*>(native_event);
   DCHECK(event->IsKeyEvent());
   return event->key_code();
 }
 
 const char* CodeFromNative(const base::NativeEvent& native_event) {
@@ skipping 149 matching lines @@
     callback.Run(&touch_event);
   } else if (native_ui_event->IsScrollEvent()) {
     ui::ScrollEvent scroll_event(native_event);
     callback.Run(&scroll_event);
   } else {
     NOTREACHED();
   }
 }
 
 }  // namespace ui