cc: Add more traces to checker imaging / image hijack code paths.

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 c8113d4d56052edb486948d64999a2680ce952d8..0d19404071806701c86bde12e52050d726aa7f85 100644
--- a/cc/tiles/checker_image_tracker.cc
+++ b/cc/tiles/checker_image_tracker.cc
@@ -39,6 +39,9 @@ void CheckerImageTracker::FilterImagesForCheckeringForTile(
     std::vector<DrawImage>* images,
     ImageIdFlatSet* checkered_images,
     WhichTree tree) {
+  TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "CheckerImageTracker::FilterImagesForCheckeringForTile", "tree",
+               tree);
   DCHECK(checkered_images->empty());
 
   auto images_to_checker = std::remove_if(
@@ -57,6 +60,8 @@ void CheckerImageTracker::FilterImagesForCheckeringForTile(
 }
 
 const ImageIdFlatSet& CheckerImageTracker::TakeImagesToInvalidateOnSyncTree() {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "CheckerImageTracker::TakeImagesToInvalidateOnSyncTree");
   DCHECK_EQ(invalidated_images_on_current_sync_tree_.size(), 0u)
       << "Sync tree can not be invalidated more than once";
 
@@ -66,6 +71,8 @@ const ImageIdFlatSet& CheckerImageTracker::TakeImagesToInvalidateOnSyncTree() {
 }
 
 void CheckerImageTracker::DidActivateSyncTree() {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "CheckerImageTracker::DidActivateSyncTree");
   for (auto image_id : invalidated_images_on_current_sync_tree_) {
     auto it = image_id_to_decode_request_id_.find(image_id);
     image_controller_->UnlockImageDecode(it->second);
@@ -79,6 +86,8 @@ void CheckerImageTracker::DidFinishImageDecode(
     ImageId image_id,
     ImageController::ImageDecodeRequestId request_id,
     ImageController::ImageDecodeResult result) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),

[Khushal, 2017/03/14 20:15:19]

Is the async one we already have here not enough?

[vmpstr, 2017/03/14 20:28:27]

It appears in a different spot in the timeline view, so it would be nice to see
where it corresponds on the thread.

+               "CheckerImageTracker::DidFinishImageDecode");
   TRACE_EVENT_ASYNC_END0("cc", "CheckerImageTracker::DeferImageDecode",
                          image_id);
 
@@ -131,6 +140,8 @@ bool CheckerImageTracker::ShouldCheckerImage(const sk_sp<const SkImage>& image,
 
 void CheckerImageTracker::ScheduleImageDecodeIfNecessary(
     const sk_sp<const SkImage>& image) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("cc.debug"),
+               "CheckerImageTracker::ScheduleImageDecodeIfNecessary");
   ImageId image_id = image->uniqueID();
 
   // If the image has already been decoded, or a decode request is pending, we