Enable disabling WebCore::GraphicsContext in telemetry.

cc/resources/picture_unittest.cc

Index: cc/resources/picture_unittest.cc
diff --git a/cc/resources/picture_unittest.cc b/cc/resources/picture_unittest.cc
index 8a36743928e72b3ad3269d582f9fe4cf2597e8b8..1a2bf0d8a78fb13f13b69e316b6f3e767adf869e 100644
--- a/cc/resources/picture_unittest.cc
+++ b/cc/resources/picture_unittest.cc
@@ -480,7 +480,7 @@ TEST(PictureTest, RecordingModes) {
                             false,
                             0,
                             Picture::RECORD_WITH_PAINTING_DISABLED);
-  EXPECT_EQ(NULL, content_layer_client.last_canvas());
+  EXPECT_TRUE(content_layer_client.last_canvas() != NULL);

[Sami, 2014/04/29 10:57:23]

Could we also check that content_layer_client was told to disable the graphics
context?

[Stephen Chennney, 2014/04/29 20:30:45]

There is no way to get to the context to ask it if it is disables. We could
maybe check that nothing has been drawn, but that is dangerous as some other
code might draw into the canvas outside of GraphicsContext.

[Sami, 2014/04/29 20:47:48]

I was more thinking of extending cc's FakeContentLayerClient to keep track of
whether it was asked to disable the context or not.

   EXPECT_TRUE(picture);
 
   EXPECT_EQ(3, Picture::RECORDING_MODE_COUNT);