cc: Remove cc::Thread and cc::ThreadImpl.

cc/trees/proxy.h

Index: cc/trees/proxy.h
diff --git a/cc/trees/proxy.h b/cc/trees/proxy.h
index aaab7802e366bd2786c34039733ee08921dcc3a3..5ab0859dc0214aea4ae015a2b7dec7abf3c72282 100644
--- a/cc/trees/proxy.h
+++ b/cc/trees/proxy.h
@@ -7,6 +7,7 @@
 
 #include "base/basictypes.h"
 #include "base/logging.h"
+#include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time.h"
 #include "base/values.h"
@@ -14,6 +15,8 @@
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkPicture.h"
 
+namespace base { class SingleThreadTaskRunner; }
+
 namespace gfx {
 class Rect;
 class Vector2d;
@@ -22,20 +25,15 @@ class Vector2d;
 namespace cc {
 
 class OutputSurface;
-class Thread;
 struct RendererCapabilities;
 
 // Abstract class responsible for proxying commands from the main-thread side of
 // the compositor over to the compositor implementation.
 class CC_EXPORT Proxy {
  public:
-  Thread* MainThread() const;
+  base::SingleThreadTaskRunner* MainThreadTaskRunner() const;
   bool HasImplThread() const;
-  Thread* ImplThread() const;
-
-  // Returns 0 if the current thread is neither the main thread nor the impl
-  // thread.
-  Thread* CurrentThread() const;
+  base::SingleThreadTaskRunner* ImplThreadTaskRunner() const;
 
   // Debug hooks.
   bool IsMainThread() const;
@@ -100,14 +98,15 @@ class CC_EXPORT Proxy {
   virtual bool CommitPendingForTesting() = 0;
 
  protected:
-  explicit Proxy(scoped_ptr<Thread> impl_thread);
+  explicit Proxy(
+      scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner);
   friend class DebugScopedSetImplThread;
   friend class DebugScopedSetMainThread;
   friend class DebugScopedSetMainThreadBlocked;
 
  private:
-  scoped_ptr<Thread> main_thread_;
-  scoped_ptr<Thread> impl_thread_;
+  scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner_;
 #ifndef NDEBUG
   bool impl_thread_is_overridden_;
   bool is_main_thread_blocked_;