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

cc/tiles/checker_image_tracker.cc

Index: cc/tiles/checker_image_tracker.cc
diff --git a/cc/tiles/checker_image_tracker.cc b/cc/tiles/checker_image_tracker.cc
index c081132e6ece23c5e9569af2dc37968d9e69e5cb..898da6d196a9812f86ad10fe91b0bf8fad2beaf4 100644
--- a/cc/tiles/checker_image_tracker.cc
+++ b/cc/tiles/checker_image_tracker.cc
@@ -77,7 +77,8 @@ void CheckerImageTracker::DidActivateSyncTree() {
 
 void CheckerImageTracker::DidFinishImageDecode(
     ImageId image_id,
-    ImageController::ImageDecodeRequestId request_id) {
+    ImageController::ImageDecodeRequestId request_id,
+    ImageController::ImageDecodeResult result) {

[Khushal, 2017/02/25 00:21:40]

May be DCHECK here that we never get decode not required, because in that case
we never should have queued a decode.

[vmpstr, 2017/02/27 21:25:28]

Done.

   TRACE_EVENT_ASYNC_END0("cc", "CheckerImageTracker::DeferImageDecode",
                          image_id);