cc: Use an enum for tracking images vetoed for async decodes.

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 8bbcbebe839fa490a47fe1e2d405598781a43ffb..8aa2a290b2527f1ec86f231a4a55b24df209fb1d 100644
--- a/cc/tiles/checker_image_tracker.cc
+++ b/cc/tiles/checker_image_tracker.cc
@@ -92,15 +92,17 @@ void CheckerImageTracker::DidFinishImageDecode(
 
   DCHECK_NE(result, ImageController::ImageDecodeResult::DECODE_NOT_REQUIRED);
   DCHECK_NE(pending_image_decodes_.count(image_id), 0u);
+  DCHECK_NE(image_async_decode_state_.count(image_id), 0u);
+
   pending_image_decodes_.erase(image_id);
 
-  images_decoded_once_.insert(image_id);
+  image_async_decode_state_[image_id] = AsyncDecodeVetoState::SYNC_DECODED_ONCE;
   images_pending_invalidation_.insert(image_id);
   client_->NeedsInvalidationForCheckerImagedTiles();
 }
 
 bool CheckerImageTracker::ShouldCheckerImage(const sk_sp<const SkImage>& image,
-                                             WhichTree tree) const {
+                                             WhichTree tree) {
   TRACE_EVENT1("cc", "CheckerImageTracker::ShouldCheckerImage", "image_id",
                image->uniqueID());
 
@@ -115,12 +117,6 @@ bool CheckerImageTracker::ShouldCheckerImage(const sk_sp<const SkImage>& image,
     return true;
   }
 
-  // If a decode request is pending for this image, continue checkering it.
-  if (pending_image_decodes_.find(image->uniqueID()) !=
-      pending_image_decodes_.end()) {
-    return true;
-  }
-
   // If the image is pending invalidation, continue checkering it. All tiles
   // for these images will be invalidated on the next pending tree.
   if (images_pending_invalidation_.find(image->uniqueID()) !=
@@ -128,13 +124,16 @@ bool CheckerImageTracker::ShouldCheckerImage(const sk_sp<const SkImage>& image,
     return true;
   }
 
-  // If the image has been decoded once before, don't checker it again.
-  if (images_decoded_once_.find(image->uniqueID()) !=
-      images_decoded_once_.end()) {
-    return false;
+  ImageId image_id = image->uniqueID();
+  if (image_async_decode_state_.find(image_id) ==
+      image_async_decode_state_.end()) {
+    image_async_decode_state_[image_id] =
+        SafeSizeOfImage(image.get()) >= kMinImageSizeToCheckerBytes
+            ? AsyncDecodeVetoState::ASYNC
+            : AsyncDecodeVetoState::SYNC_PERMANENT;
   }
 
-  return SafeSizeOfImage(image.get()) >= kMinImageSizeToCheckerBytes;
+  return image_async_decode_state_[image_id] == AsyncDecodeVetoState::ASYNC;

[vmpstr, 2017/04/11 18:42:55]

Erm, in lines 128-136 you do 3 finds on the same image. Can you cache some of
the results

[Khushal, 2017/04/12 20:31:17]

Done.

 }
 
 void CheckerImageTracker::ScheduleImageDecodeIfNecessary(
@@ -143,10 +142,14 @@ void CheckerImageTracker::ScheduleImageDecodeIfNecessary(
                "CheckerImageTracker::ScheduleImageDecodeIfNecessary");
   ImageId image_id = image->uniqueID();
 
-  // If the image has already been decoded, or a decode request is pending, we
-  // don't need to schedule another decode.
-  if (images_decoded_once_.count(image_id) != 0 ||
-      pending_image_decodes_.count(image_id) != 0) {
+  // The image might have already been decoded, in which case we don't need to

[vmpstr, 2017/04/11 18:42:55]

Can you reword the comment to take into account that we're not checking whether
it's been decoded, rather we're checking if it can be async

[Khushal, 2017/04/12 20:31:17]

Done.

+  // request another decode.
+  DCHECK_NE(image_async_decode_state_.count(image_id), 0u);
+  if (image_async_decode_state_[image_id] != AsyncDecodeVetoState::ASYNC)
+    return;
+
+  // If a decode request is pending, we don't need to schedule another decode.
+  if (pending_image_decodes_.count(image_id) != 0) {
     return;
   }