cc: Add readback and forced draw states to the Scheduler

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 9afe3c4f8cf8e0d1b5e0d2644d50efdbc173f97a..4f092663ee19bbb41197ae08c37177c4d257dba2 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -375,6 +375,12 @@ void LayerTreeTest::PostSetNeedsCommitToMainThread() {
                  main_thread_weak_ptr_));
 }
 
+void LayerTreeTest::PostReadbackToMainThread() {
+  proxy()->MainThreadTaskRunner()->PostTask(
+      FROM_HERE,
+      base::Bind(&LayerTreeTest::DispatchReadback, main_thread_weak_ptr_));
+}
+
 void LayerTreeTest::PostAcquireLayerTextures() {
   proxy()->MainThreadTaskRunner()->PostTask(
       FROM_HERE,
@@ -504,6 +510,15 @@ void LayerTreeTest::DispatchSetNeedsCommit() {
     layer_tree_host_->SetNeedsCommit();
 }
 
+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::DispatchAcquireLayerTextures() {
   DCHECK(!proxy() || proxy()->IsMainThread());