Support single-threaded impl-side painting

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 8c0255af03112cfa65e55d67314e049f880ca2a3..ef6ed71ddff910bc4537052147bc19a62a911b70 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -514,6 +514,13 @@ void LayerTreeTest::PostSetNextCommitForcesRedrawToMainThread() {
                  main_thread_weak_ptr_));
 }
 
+void LayerTreeTest::PostCompositeImmediatelyToMainThread() {
+  main_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&LayerTreeTest::DispatchCompositeImmediately,
+                 main_thread_weak_ptr_));
+}
+
 void LayerTreeTest::WillBeginTest() {
   layer_tree_host_->SetLayerTreeHostClientReady();
 }
@@ -629,6 +636,12 @@ void LayerTreeTest::DispatchSetNextCommitForcesRedraw() {
     layer_tree_host_->SetNextCommitForcesRedraw();
 }
 
+void LayerTreeTest::DispatchCompositeImmediately() {
+  DCHECK(!proxy() || proxy()->IsMainThread());
+  if (layer_tree_host_)
+    layer_tree_host_->Composite(gfx::FrameTime::Now());
+}
+
 void LayerTreeTest::RunTest(bool threaded,
                             bool delegating_renderer,
                             bool impl_side_painting) {