[exp] cc: Introduce cc::CompositorMutator.

cc/trees/layer_tree_host_unittest.cc

Index: cc/trees/layer_tree_host_unittest.cc
diff --git a/cc/trees/layer_tree_host_unittest.cc b/cc/trees/layer_tree_host_unittest.cc
index aacabd717ef2d15f27021033001f86756fba9448..e23943f8944fc523ef1374af5dc75dfa2d9739fa 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -2084,7 +2084,7 @@ class LayerTreeHostWithProxy : public LayerTreeHost {
   LayerTreeHostWithProxy(FakeLayerTreeHostClient* client,
                          const LayerTreeSettings& settings,
                          scoped_ptr<FakeProxy> proxy)
-      : LayerTreeHost(client, NULL, NULL, settings) {
+      : LayerTreeHost(client, NULL, NULL, NULL, settings) {
     proxy->SetLayerTreeHost(this);
     client->SetLayerTreeHost(this);
     InitializeForTesting(proxy.Pass());
@@ -2156,14 +2156,9 @@ TEST(LayerTreeHostTest, PartialUpdatesWithGLRenderer) {
 
   scoped_ptr<SharedBitmapManager> shared_bitmap_manager(
       new TestSharedBitmapManager());
-  scoped_ptr<LayerTreeHost> host =
-      LayerTreeHost::CreateSingleThreaded(&client,
-                                          &client,
-                                          shared_bitmap_manager.get(),
-                                          NULL,
-                                          settings,
-                                          base::MessageLoopProxy::current(),
-                                          nullptr);
+  scoped_ptr<LayerTreeHost> host = LayerTreeHost::CreateSingleThreaded(
+      &client, &client, shared_bitmap_manager.get(), NULL, nullptr, settings,
+      base::MessageLoopProxy::current(), nullptr);
   client.SetLayerTreeHost(host.get());
   host->Composite(base::TimeTicks::Now());
 
@@ -2180,14 +2175,9 @@ TEST(LayerTreeHostTest, PartialUpdatesWithSoftwareRenderer) {
 
   scoped_ptr<SharedBitmapManager> shared_bitmap_manager(
       new TestSharedBitmapManager());
-  scoped_ptr<LayerTreeHost> host =
-      LayerTreeHost::CreateSingleThreaded(&client,
-                                          &client,
-                                          shared_bitmap_manager.get(),
-                                          NULL,
-                                          settings,
-                                          base::MessageLoopProxy::current(),
-                                          nullptr);
+  scoped_ptr<LayerTreeHost> host = LayerTreeHost::CreateSingleThreaded(
+      &client, &client, shared_bitmap_manager.get(), NULL, nullptr, settings,
+      base::MessageLoopProxy::current(), nullptr);
   client.SetLayerTreeHost(host.get());
   host->Composite(base::TimeTicks::Now());
 
@@ -2204,14 +2194,9 @@ TEST(LayerTreeHostTest, PartialUpdatesWithDelegatingRendererAndGLContent) {
 
   scoped_ptr<SharedBitmapManager> shared_bitmap_manager(
       new TestSharedBitmapManager());
-  scoped_ptr<LayerTreeHost> host =
-      LayerTreeHost::CreateSingleThreaded(&client,
-                                          &client,
-                                          shared_bitmap_manager.get(),
-                                          NULL,
-                                          settings,
-                                          base::MessageLoopProxy::current(),
-                                          nullptr);
+  scoped_ptr<LayerTreeHost> host = LayerTreeHost::CreateSingleThreaded(
+      &client, &client, shared_bitmap_manager.get(), NULL, nullptr, settings,
+      base::MessageLoopProxy::current(), nullptr);
   client.SetLayerTreeHost(host.get());
   host->Composite(base::TimeTicks::Now());
 
@@ -2229,14 +2214,9 @@ TEST(LayerTreeHostTest,
 
   scoped_ptr<SharedBitmapManager> shared_bitmap_manager(
       new TestSharedBitmapManager());
-  scoped_ptr<LayerTreeHost> host =
-      LayerTreeHost::CreateSingleThreaded(&client,
-                                          &client,
-                                          shared_bitmap_manager.get(),
-                                          NULL,
-                                          settings,
-                                          base::MessageLoopProxy::current(),
-                                          nullptr);
+  scoped_ptr<LayerTreeHost> host = LayerTreeHost::CreateSingleThreaded(
+      &client, &client, shared_bitmap_manager.get(), NULL, nullptr, settings,
+      base::MessageLoopProxy::current(), nullptr);
   client.SetLayerTreeHost(host.get());
   host->Composite(base::TimeTicks::Now());