Support single-threaded impl-side painting

cc/test/layer_tree_pixel_test.cc

Index: cc/test/layer_tree_pixel_test.cc
diff --git a/cc/test/layer_tree_pixel_test.cc b/cc/test/layer_tree_pixel_test.cc
index 31d30a4b676ffa627c501a922a00f0d735234818..8b6f5ddb6fc9f54a90954fed60f2e930193d4dcd 100644
--- a/cc/test/layer_tree_pixel_test.cc
+++ b/cc/test/layer_tree_pixel_test.cc
@@ -197,7 +197,20 @@ void LayerTreePixelTest::RunPixelTest(
   content_root_ = content_root;
   readback_target_ = NULL;
   ref_file_ = file_name;
-  RunTest(true, false, impl_side_painting_);
+  bool threaded = true;
+  RunTest(threaded, false, impl_side_painting_);
+}
+
+void LayerTreePixelTest::RunSingleThreadedPixelTest(
+    PixelTestType test_type,
+    scoped_refptr<Layer> content_root,
+    base::FilePath file_name) {
+  test_type_ = test_type;
+  content_root_ = content_root;
+  readback_target_ = NULL;
+  ref_file_ = file_name;
+  bool threaded = false;
+  RunTest(threaded, false, impl_side_painting_);
 }
 
 void LayerTreePixelTest::RunPixelTestWithReadbackTarget(