ui/events: Add changed_button_flags_ in ui::PointerEvent.

ui/events/mojo/event.mojom

 // 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.
 
 module ui.mojom;
 
 import "ui/events/mojo/event_constants.mojom";
 import "ui/events/mojo/keyboard_codes.mojom";
 
 struct KeyData {
@@ skipping 45 matching lines @@
   float y;
   // |screen_x| and |screen_y| are in screen coordinates in units of
   // physical pixels.
   float screen_x;
   float screen_y;
 };
 
 // TODO(rjkroege,sadrul): Add gesture representation.
 struct PointerData {
   int32 pointer_id;
+  int32 changed_button_flags;
   PointerKind kind;
   LocationData location;
   // Some devices (e.g. pen, finger) can extend across multiple pixels
   // at once. |brush_data| provides additional data for this case and
   // is available when |kind| is PEN or TOUCH.
   BrushData? brush_data;
   // Only set for |WHEEL| events.
   WheelData? wheel_data;
 };
 
@@ skipping 34 matching lines @@
   //
   // TODO(sky): parts of this should move to PointerData.
   int32 flags;
   // Time in microseconds from when the platform was started.
   // This value accurately orders events w.r.t. to each other but
   // does not position them at an absolute time.
   int64 time_stamp;
   KeyData? key_data;
   PointerData? pointer_data;
 };