cc: Make image controller return a status with the callback.

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 60a4843854f8af1b44d7f11e8967ef628dde71bb..a60bcf75f5b4e2cdef444d4ad05e27b240577402 100644
--- a/cc/tiles/checker_image_tracker_unittest.cc
+++ b/cc/tiles/checker_image_tracker_unittest.cc
@@ -48,7 +48,9 @@ class TestImageController : public ImageController {
 
     // Post the callback asynchronously to match the behaviour in
     // ImageController.
-    worker_task_runner_->PostTask(FROM_HERE, base::Bind(callback, request_id));
+    worker_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(callback, request_id, ImageDecodeResult::SUCCESS));
 
     return request_id;
   }