cc: Commit directly to active tree when using single thread.

cc/test/fake_proxy.cc

Index: cc/test/fake_proxy.cc
diff --git a/cc/test/fake_proxy.cc b/cc/test/fake_proxy.cc
index 4490c7607ce6849af251ec964040a160b847470d..f5fc886b5af15b14aeab5e6152fb9532395062a7 100644
--- a/cc/test/fake_proxy.cc
+++ b/cc/test/fake_proxy.cc
@@ -12,6 +12,10 @@ void FakeProxy::SetLayerTreeHost(LayerTreeHost* host) {
 
 bool FakeProxy::IsStarted() const { return true; }
 
+bool FakeProxy::CommitToActiveTree() const {
+  return false;
+}
+
 const RendererCapabilities& FakeProxy::GetRendererCapabilities() const {
   return capabilities_;
 }