Remove CompositeAndReadback from LayerTreeHost(Impl) and the Proxys.

cc/test/layer_tree_test.cc

Index: cc/test/layer_tree_test.cc
diff --git a/cc/test/layer_tree_test.cc b/cc/test/layer_tree_test.cc
index 2a0762d39cccda553f015b318ba79ea8711e8bd5..8a80f89121f978c542c7152fb43738f91ac0acc5 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -108,10 +108,8 @@ class LayerTreeHostImplForTesting : public LayerTreeHostImpl {
     }
   }
 
-  virtual DrawResult PrepareToDraw(FrameData* frame,
-                                   const gfx::Rect& damage_rect) OVERRIDE {
-    DrawResult draw_result =
-        LayerTreeHostImpl::PrepareToDraw(frame, damage_rect);
+  virtual DrawResult PrepareToDraw(FrameData* frame) OVERRIDE {
+    DrawResult draw_result = LayerTreeHostImpl::PrepareToDraw(frame);
     return test_hooks_->PrepareToDrawOnThread(this, frame, draw_result);
   }
 
@@ -417,12 +415,6 @@ void LayerTreeTest::PostSetNeedsUpdateLayersToMainThread() {
                  main_thread_weak_ptr_));
 }
 
-void LayerTreeTest::PostReadbackToMainThread() {
-  main_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&LayerTreeTest::DispatchReadback, main_thread_weak_ptr_));
-}
-
 void LayerTreeTest::PostSetNeedsRedrawToMainThread() {
   main_task_runner_->PostTask(FROM_HERE,
                               base::Bind(&LayerTreeTest::DispatchSetNeedsRedraw,
@@ -548,15 +540,6 @@ void LayerTreeTest::DispatchSetNeedsUpdateLayers() {
     layer_tree_host_->SetNeedsUpdateLayers();
 }
 
-void LayerTreeTest::DispatchReadback() {
-  DCHECK(!proxy() || proxy()->IsMainThread());
-
-  if (layer_tree_host_) {
-    char pixels[4];
-    layer_tree_host()->CompositeAndReadback(&pixels, gfx::Rect(0, 0, 1, 1));
-  }
-}
-
 void LayerTreeTest::DispatchSetNeedsRedraw() {
   DCHECK(!proxy() || proxy()->IsMainThread());