[exp] cc: Introduce cc::CompositorMutator.

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index 8056387b2f213d2004b59f82a015d240497098e5..91828cce0807e7fee60c3578047353a6def9f6b9 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -167,13 +167,10 @@ class LayerTreeHostImplTest : public testing::Test,
 
   virtual bool CreateHostImpl(const LayerTreeSettings& settings,
                               scoped_ptr<OutputSurface> output_surface) {
-    host_impl_ = LayerTreeHostImpl::Create(settings,
-                                           this,
-                                           &proxy_,
-                                           &stats_instrumentation_,
-                                           shared_bitmap_manager_.get(),
-                                           gpu_memory_buffer_manager_.get(),
-                                           0);
+    host_impl_ = LayerTreeHostImpl::Create(
+        settings, this, &proxy_, &stats_instrumentation_,
+        shared_bitmap_manager_.get(), gpu_memory_buffer_manager_.get(), nullptr,
+        0);
     bool init = host_impl_->InitializeRenderer(output_surface.Pass());
     host_impl_->SetViewportSize(gfx::Size(10, 10));
     return init;
@@ -1548,6 +1545,7 @@ class LayerTreeHostImplOverridePhysicalTime : public LayerTreeHostImpl {
                           rendering_stats_instrumentation,
                           manager,
                           NULL,
+                          NULL,
                           0) {}
 
   BeginFrameArgs CurrentBeginFrameArgs() const override {
@@ -5050,13 +5048,9 @@ TEST_F(LayerTreeHostImplTest, PartialSwapReceivesDamageRect) {
   scoped_ptr<SharedBitmapManager> shared_bitmap_manager(
       new TestSharedBitmapManager());
   scoped_ptr<LayerTreeHostImpl> layer_tree_host_impl =
-      LayerTreeHostImpl::Create(settings,
-                                this,
-                                &proxy_,
+      LayerTreeHostImpl::Create(settings, this, &proxy_,
                                 &stats_instrumentation_,
-                                shared_bitmap_manager.get(),
-                                NULL,
-                                0);
+                                shared_bitmap_manager.get(), nullptr, NULL, 0);
   layer_tree_host_impl->InitializeRenderer(output_surface.Pass());
   layer_tree_host_impl->SetViewportSize(gfx::Size(500, 500));
 
@@ -5344,7 +5338,7 @@ static scoped_ptr<LayerTreeHostImpl> SetupLayersForOpacity(
   LayerTreeSettings settings;
   settings.renderer_settings.partial_swap_enabled = partial_swap;
   scoped_ptr<LayerTreeHostImpl> my_host_impl = LayerTreeHostImpl::Create(
-      settings, client, proxy, stats_instrumentation, manager, NULL, 0);
+      settings, client, proxy, stats_instrumentation, manager, NULL, NULL, 0);
   my_host_impl->InitializeRenderer(output_surface.Pass());
   my_host_impl->SetViewportSize(gfx::Size(100, 100));
 
@@ -6670,13 +6664,10 @@ TEST_F(LayerTreeHostImplTestDeferredInitialize, Fails) {
 // doesn't support memory management extensions.
 TEST_F(LayerTreeHostImplTest, DefaultMemoryAllocation) {
   LayerTreeSettings settings;
-  host_impl_ = LayerTreeHostImpl::Create(settings,
-                                         this,
-                                         &proxy_,
-                                         &stats_instrumentation_,
-                                         shared_bitmap_manager_.get(),
-                                         gpu_memory_buffer_manager_.get(),
-                                         0);
+  host_impl_ = LayerTreeHostImpl::Create(
+      settings, this, &proxy_, &stats_instrumentation_,
+      shared_bitmap_manager_.get(), gpu_memory_buffer_manager_.get(), nullptr,
+      0);
 
   scoped_ptr<OutputSurface> output_surface(
       FakeOutputSurface::Create3d(TestWebGraphicsContext3D::Create()));
@@ -6717,7 +6708,7 @@ TEST_F(LayerTreeHostImplTest, MemoryPolicy) {
   LayerTreeSettings settings;
   settings.gpu_rasterization_enabled = true;
   host_impl_ = LayerTreeHostImpl::Create(
-      settings, this, &proxy_, &stats_instrumentation_, NULL, NULL, 0);
+      settings, this, &proxy_, &stats_instrumentation_, NULL, NULL, NULL, 0);
   host_impl_->SetUseGpuRasterization(true);
   host_impl_->SetVisible(true);
   host_impl_->SetMemoryPolicy(policy1);