[wip/exp] cc: Measure the amount of overdraw.

ash/test/ash_test_helper.cc

Index: ash/test/ash_test_helper.cc
diff --git a/ash/test/ash_test_helper.cc b/ash/test/ash_test_helper.cc
index b5b6f5d6b95a1a46d8ef8551b95fffc5ebbb72e5..4216db937d5cb39e129943cbf8e381c96b417409 100644
--- a/ash/test/ash_test_helper.cc
+++ b/ash/test/ash_test_helper.cc
@@ -361,7 +361,7 @@ void AshTestHelper::CreateShell() {
   CHECK(config_ == Config::CLASSIC);
   ui::ContextFactory* context_factory = nullptr;
   ui::ContextFactoryPrivate* context_factory_private = nullptr;
-  bool enable_pixel_output = false;
+  bool enable_pixel_output = true;
   ui::InitializeContextFactoryForTests(enable_pixel_output, &context_factory,
                                        &context_factory_private);
   ShellInitParams init_params;