Disable UI compositor partial swaps on Mac

ui/compositor/compositor.cc

 // Copyright (c) 2012 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/compositor/compositor.h"
 
 #include <algorithm>
 #include <deque>
 
 #include "base/bind.h"
@@ skipping 82 matching lines @@
 
   cc::LayerTreeSettings settings;
   settings.refresh_rate =
       context_factory_->DoesCreateTestContexts()
       ? kTestRefreshRate
       : kDefaultRefreshRate;
   settings.main_frame_before_draw_enabled = false;
   settings.main_frame_before_activation_enabled = false;
   settings.throttle_frame_production =
       !command_line->HasSwitch(switches::kDisableGpuVsync);
+#if !defined(OS_MACOSX)
   settings.partial_swap_enabled =
       !command_line->HasSwitch(cc::switches::kUIDisablePartialSwap);
+#endif
 #if defined(OS_CHROMEOS)
   settings.per_tile_painting_enabled = true;
 #endif
 
   // These flags should be mirrored by renderer versions in content/renderer/.
   settings.initial_debug_state.show_debug_borders =
       command_line->HasSwitch(cc::switches::kUIShowCompositedLayerBorders);
   settings.initial_debug_state.show_fps_counter =
       command_line->HasSwitch(cc::switches::kUIShowFPSCounter);
   settings.initial_debug_state.show_layer_animation_bounds_rects =
@@ skipping 288 matching lines @@
     // CompositorObservers to be notified before starting another
     // draw cycle.
     ScheduleDraw();
   }
   FOR_EACH_OBSERVER(CompositorObserver,
                     observer_list_,
                     OnCompositingEnded(this));
 }
 
 }  // namespace ui