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 60e8035f6f978a567547f82582269de49257dd77..0112e4d320854452363b31270ceaf11c1573e935 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -109,10 +109,9 @@ class LayerTreeHostImplForTesting : public LayerTreeHostImpl {
   }
 
   virtual DrawSwapReadbackResult::DrawResult PrepareToDraw(
-      FrameData* frame,
-      const gfx::Rect& damage_rect) OVERRIDE {
+      FrameData* frame) OVERRIDE {
     DrawSwapReadbackResult::DrawResult draw_result =
-        LayerTreeHostImpl::PrepareToDraw(frame, damage_rect);
+        LayerTreeHostImpl::PrepareToDraw(frame);
     return test_hooks_->PrepareToDrawOnThread(this, frame, draw_result);
   }
 
@@ -418,12 +417,6 @@ 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,
@@ -549,15 +542,6 @@ 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());