cc: Move pre-decodes to background worker.

cc/tiles/checker_image_tracker_unittest.cc

Index: cc/tiles/checker_image_tracker_unittest.cc
diff --git a/cc/tiles/checker_image_tracker_unittest.cc b/cc/tiles/checker_image_tracker_unittest.cc
index a0dd0225895fd877f216240192926711799e115f..69c346f335b1f017054a8d8db3dbbe7d0842ecc2 100644
--- a/cc/tiles/checker_image_tracker_unittest.cc
+++ b/cc/tiles/checker_image_tracker_unittest.cc
@@ -121,7 +121,8 @@ class CheckerImageTrackerTest : public testing::Test,
     CheckerImageTracker::ImageDecodeQueue decode_queue;
     for (const auto& image : images) {
       if (checker_image_tracker_->ShouldCheckerImage(image, tree))
-        decode_queue.push_back(image.paint_image());
+        decode_queue.push_back(CheckerImageTracker::ImageDecodeRequest(
+            image.paint_image(), CheckerImageTracker::DecodeType::kRaster));
     }
     return decode_queue;
   }
@@ -169,8 +170,8 @@ TEST_F(CheckerImageTrackerTest, UpdatesImagesAtomically) {
       BuildImageDecodeQueue(draw_images, WhichTree::PENDING_TREE);
 
   ASSERT_EQ(2u, image_decode_queue.size());
-  EXPECT_EQ(checkerable_image.paint_image(), image_decode_queue[0]);
-  EXPECT_EQ(checkerable_image.paint_image(), image_decode_queue[1]);
+  EXPECT_EQ(checkerable_image.paint_image(), image_decode_queue[0].paint_image);
+  EXPECT_EQ(checkerable_image.paint_image(), image_decode_queue[1].paint_image);
 
   checker_image_tracker_->ScheduleImageDecodeQueue(image_decode_queue);
   EXPECT_EQ(image_controller_.num_of_locked_images(), 1);
@@ -415,7 +416,7 @@ TEST_F(CheckerImageTrackerTest, CheckersOnlyStaticCompletedImages) {
   CheckerImageTracker::ImageDecodeQueue image_decode_queue =
       BuildImageDecodeQueue(draw_images, WhichTree::PENDING_TREE);
   EXPECT_EQ(image_decode_queue.size(), 1U);
-  EXPECT_EQ(image_decode_queue[0], static_image.paint_image());
+  EXPECT_EQ(image_decode_queue[0].paint_image, static_image.paint_image());
 
   // Change the partial image to complete and try again. It should sstill not
   // be checkered.