cc: Drop locked decodes from checker image tracker on cache switch.

cc/tiles/checker_image_tracker.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_TILES_CHECKER_IMAGE_TRACKER_H_
 #define CC_TILES_CHECKER_IMAGE_TRACKER_H_
 
 #include <unordered_map>
 #include <vector>
 
@@ skipping 48 matching lines @@
   void ClearTracker(bool can_clear_decode_policy_tracking);
 
   // Informs the tracker to not checker the given image. This can be used to opt
   // out of the checkering behavior for certain images, such as ones that were
   // decoded using the img.decode api.
   // Note that if the image is already being checkered, then it will continue to
   // do so. This call is meant to be issued prior to the image appearing during
   // raster.
   void DisallowCheckeringForImage(const PaintImage& image);
 
+  bool has_locked_decodes_for_testing() const {
+    return !image_id_to_decode_.empty();
+  }
+
  private:
   enum class DecodePolicy {
     // The image can be decoded asynchronously from raster. When set, the image
     // is always skipped during rasterization of content that includes this
     // image until it has been decoded using the decode service.
     ASYNC,
     // The image has been decoded asynchronously once and should now be
     // synchronously rasterized with the content or the image has been
     // permanently vetoed from being decoded async.
     SYNC
@@ skipping 63 matching lines @@
       image_id_to_decode_;
 
   base::WeakPtrFactory<CheckerImageTracker> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CheckerImageTracker);
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_CHECKER_IMAGE_TRACKER_H_