Update from https://crrev.com/320931

cc/resources/tile_manager.cc

Index: cc/resources/tile_manager.cc
diff --git a/cc/resources/tile_manager.cc b/cc/resources/tile_manager.cc
index 00ae3da6e92fed3b9a96a0d8e5b781df8541b4d8..7ea86f00c442ab1c0a4909a2197fffbcca6b1efe 100644
--- a/cc/resources/tile_manager.cc
+++ b/cc/resources/tile_manager.cc
@@ -148,6 +148,10 @@ class ImageDecodeTaskImpl : public ImageDecodeTask {
     // This will cause the image referred to by pixel ref to be decoded.
     pixel_ref_->lockPixels();
     pixel_ref_->unlockPixels();
+
+    // Release the reference after decoding image to ensure that it is not
+    // kept alive unless needed.
+    pixel_ref_.clear();
   }
 
   // Overridden from TileTask: