Disable region copy on ARM since it isn't supported

ui/ozone/platform/drm/gpu/drm_surface.cc

 // 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/ozone/platform/drm/gpu/drm_surface.h"
 
 #include "base/bind_helpers.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "third_party/skia/include/core/SkCanvas.h"
@@ skipping 81 matching lines @@
   canvas->drawImageRect(pending_image_.get(), &real_damage, real_damage, NULL);
   last_damage_ = pending_image_damage_;
 
   pending_image_ = nullptr;
   pending_image_damage_ = gfx::Rect();
 
   window_->QueueOverlayPlane(OverlayPlane(back_buffer_));
 
   // Update our front buffer pointer.
   std::swap(front_buffer_, back_buffer_);
-  pending_pageflip_ = window_->SchedulePageFlip(
-      false /* is_sync */,
-      base::Bind(&DrmSurface::OnPageFlip, weak_ptr_factory_.GetWeakPtr()));
+  // First set the pending flag otherwise there could be a re-entrancy issue if
+  // the callback is executed synchronously.
+  pending_pageflip_ = true;
+  if (!window_->SchedulePageFlip(false /* is_sync */,
+                                 base::Bind(&DrmSurface::OnPageFlip,
+                                            weak_ptr_factory_.GetWeakPtr()))) {
+    pending_pageflip_ = false;
+  }
 }
 
 void DrmSurface::OnPageFlip(gfx::SwapResult result) {
   pending_pageflip_ = false;
   if (!pending_image_)
     return;
 
   SchedulePageFlip();
 }
 
 }  // namespace ui