Use WebKit compositor in ui::Layer

ui/gfx/compositor/test_compositor.cc

Index: ui/gfx/compositor/test_compositor.cc
diff --git a/ui/gfx/compositor/test_compositor.cc b/ui/gfx/compositor/test_compositor.cc
index 311a9239b6c27ed4e1a07712803aafa3109c74d4..f34021e50710170830e005bbbd72aadaf0bf05de 100644
--- a/ui/gfx/compositor/test_compositor.cc
+++ b/ui/gfx/compositor/test_compositor.cc
@@ -40,6 +40,12 @@ void TestCompositor::OnNotifyEnd() {
 void TestCompositor::Blur(const gfx::Rect& bounds) {
 }
 
+void TestCompositor::DrawTree() {
+#if !defined(USE_WEBKIT_COMPOSITOR)
+  Compositor::DrawTree();
+#endif
+}
+
 void TestCompositor::OnWidgetSizeChanged() {
 }