cc: Remove the LayerTreeHost abstraction.

cc/trees/proxy_main.h

Index: cc/trees/proxy_main.h
diff --git a/cc/trees/proxy_main.h b/cc/trees/proxy_main.h
index 5ebf39623989dd4c969f0aa83585deb9f956058c..29f4880a8b6225dd5dda9d6c871a67c46b07f80c 100644
--- a/cc/trees/proxy_main.h
+++ b/cc/trees/proxy_main.h
@@ -16,7 +16,7 @@ namespace cc {
 class MutatorEvents;
 class CompletionEvent;
 class CompositorFrameSink;
-class LayerTreeHostInProcess;
+class LayerTreeHost;
 class LayerTreeMutator;
 class ProxyImpl;
 
@@ -25,7 +25,7 @@ class ProxyImpl;
 // The class is created and lives on the main thread.
 class CC_EXPORT ProxyMain : public Proxy {
  public:
-  ProxyMain(LayerTreeHostInProcess* layer_tree_host,
+  ProxyMain(LayerTreeHost* layer_tree_host,
             TaskRunnerProvider* task_runner_provider);
 
   ~ProxyMain() override;
@@ -98,7 +98,7 @@ class CC_EXPORT ProxyMain : public Proxy {
   void InitializeOnImplThread(CompletionEvent* completion_event);
   void DestroyProxyImplOnImplThread(CompletionEvent* completion_event);
 
-  LayerTreeHostInProcess* layer_tree_host_;
+  LayerTreeHost* layer_tree_host_;
 
   TaskRunnerProvider* task_runner_provider_;