Disable region copy on ARM since it isn't supported

ui/ozone/platform/drm/gpu/drm_window.h

 // 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.
 
 #ifndef UI_OZONE_PLATFORM_DRM_GPU_DRM_WINDOW_H_
 #define UI_OZONE_PLATFORM_DRM_GPU_DRM_WINDOW_H_
 
 #include <vector>
 
 #include "base/timer/timer.h"
@@ skipping 116 matching lines @@
   gfx::Point cursor_location_;
   int cursor_frame_ = 0;
   int cursor_frame_delay_ms_ = 0;
 
   // Planes and flips currently being queued in the absence of hardware display
   // controller.
   OverlayPlaneList pending_planes_;
   OverlayPlaneList last_submitted_planes_;
   bool last_swap_sync_ = false;
 
+  bool force_buffer_reallocation_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(DrmWindow);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRM_GPU_DRM_WINDOW_H_