cc/blimp: Eliminate Layer updates for common cases.

cc/blimp/layer_tree_host_remote_unittest.cc

 // Copyright 2016 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 "cc/blimp/layer_tree_host_remote.h"
 
 #include "base/bind.h"
 #include "base/run_loop.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "cc/animation/animation_host.h"
@@ skipping 395 matching lines @@
   // Destroy a layer and send a scroll update for it. We should be informed that
   // the update could not be applied successfully.
   child_layer1->RemoveAllChildren();
   scroll_updates.clear();
   scroll_updates[child_layer2->id()] = gfx::ScrollOffset(3, 2);
   updates_applied =
       remote_compositor_bridge_->SendUpdates(scroll_updates, new_scale_factor);
   EXPECT_FALSE(updates_applied);
 }
 
+TEST_F(LayerTreeHostRemoteTest, IdentifiedLayersToSkipUpdates) {
+  EXPECT_BEGIN_MAIN_FRAME_AND_COMMIT(mock_layer_tree_host_client_, 1);
+
+  scoped_refptr<MockLayer> non_drawable_layer = new MockLayer(true);
+  non_drawable_layer->SetIsDrawable(false);
+  non_drawable_layer->SetBounds(gfx::Size(5, 5));
+
+  scoped_refptr<MockLayer> empty_bound_layer = new MockLayer(true);

[ajuma, 2016/11/01 21:37:07]

nit: empty_bounds_layer

+  empty_bound_layer->SetIsDrawable(true);
+  empty_bound_layer->SetBounds(gfx::Size());
+
+  scoped_refptr<MockLayer> transparent_layer = new MockLayer(true);
+  transparent_layer->SetIsDrawable(true);
+  transparent_layer->SetBounds(gfx::Size(5, 5));
+  transparent_layer->SetOpacity(0.f);
+
+  scoped_refptr<MockLayer> updated_layer = new MockLayer(true);
+  updated_layer->SetIsDrawable(true);
+  updated_layer->SetBounds(gfx::Size(5, 5));
+
+  root_layer_->AddChild(non_drawable_layer);
+  root_layer_->AddChild(empty_bound_layer);
+  empty_bound_layer->SetMaskLayer(transparent_layer.get());
+  empty_bound_layer->AddChild(updated_layer);
+  DCHECK(updated_layer->GetLayerTreeHostForTesting());
+
+  // Commit and serialize.
+  layer_tree_host_->SetNeedsCommit();
+  base::RunLoop().RunUntilIdle();
+
+  // Only the updated_layer should have been updated.
+  EXPECT_FALSE(non_drawable_layer->did_update());
+  EXPECT_FALSE(empty_bound_layer->did_update());
+  EXPECT_FALSE(transparent_layer->did_update());
+  EXPECT_TRUE(updated_layer->did_update());
+}
+
 }  // namespace
 }  // namespace cc