cc: Use occlusion for deciding raster/eviction priorities in browser

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 67 matching lines @@
       locks_will_time_out_(true),
       compositor_lock_(NULL),
       layer_animator_collection_(this),
       weak_ptr_factory_(this) {
   root_web_layer_ = cc::Layer::Create(Layer::UILayerSettings());
 
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
 
   cc::LayerTreeSettings settings;
 
-  // When impl-side painting is enabled, this will ensure PictureLayers always
-  // can have LCD text, to match the previous behaviour with ContentLayers,
-  // where LCD-not-allowed notifications were ignored.
+  // This will ensure PictureLayers always can have LCD text, to match the
+  // previous behaviour with ContentLayers, where LCD-not-allowed notifications
+  // were ignored.
   settings.layers_always_allowed_lcd_text = true;
+  // Use occlusion to allow more overlapping windows to take less memory.
+  settings.use_occlusion_for_tile_prioritization = true;
   settings.renderer_settings.refresh_rate =
       context_factory_->DoesCreateTestContexts() ? kTestRefreshRate
                                                  : kDefaultRefreshRate;
   settings.main_frame_before_activation_enabled = false;
   if (command_line->HasSwitch(switches::kDisableGpuVsync)) {
     std::string display_vsync_string =
         command_line->GetSwitchValueASCII(switches::kDisableGpuVsync);
     if (display_vsync_string == "gpu") {
       settings.renderer_settings.disable_display_vsync = true;
     } else if (display_vsync_string == "beginframe") {
@@ skipping 356 matching lines @@
                     observer_list_,
                     OnCompositingLockStateChanged(this));
 }
 
 void Compositor::CancelCompositorLock() {
   if (compositor_lock_)
     compositor_lock_->CancelLock();
 }
 
 }  // namespace ui