cc: Disallow img.decode images from being checker imaged.

cc/tiles/checker_image_tracker_unittest.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/tiles/checker_image_tracker.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/run_loop.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 398 matching lines @@
   // Change the partial image to complete and try again. It should still not
   // be checkered.
   gfx::Size image_size = gfx::Size(partial_image.sk_image()->width(),
                                    partial_image.sk_image()->height());
   PaintImage completed_paint_image =
       PaintImage(partial_image.stable_id(), CreateDiscardableImage(image_size));
   EXPECT_FALSE(checker_image_tracker_->ShouldCheckerImage(
       completed_paint_image, WhichTree::PENDING_TREE));
 }
 
+TEST_F(CheckerImageTrackerTest, DontCheckerDisallowedImages) {
+  SetUpTracker(true);
+
+  PaintImage image = CreateImage(ImageType::CHECKERABLE);
+  EXPECT_TRUE(checker_image_tracker_->ShouldCheckerImage(
+      image, WhichTree::PENDING_TREE));
+  checker_image_tracker_->DisallowCheckeringForImage(image);
+  // Since the tracker already saw the image, even disallowing it would still
+  // ensure that we checker it until it's completed.
+  EXPECT_TRUE(checker_image_tracker_->ShouldCheckerImage(
+      image, WhichTree::PENDING_TREE));
+
+  // Reset the tracker.
+  checker_image_tracker_->ClearTracker(true);
+  // If we haven't seen the image and disallow it first, then it's not
+  // checkerable anymore.
+  checker_image_tracker_->DisallowCheckeringForImage(image);
+  EXPECT_FALSE(checker_image_tracker_->ShouldCheckerImage(
+      image, WhichTree::PENDING_TREE));
+}
+
 }  // namespace
 }  // namespace cc