cc: Add image decode queue functionality to image manager.

cc/tiles/image_controller.h

Index: cc/tiles/image_controller.h
diff --git a/cc/tiles/image_controller.h b/cc/tiles/image_controller.h
index d64282f8e9040c09d0deee671c90e529fa5cb3b8..aa1a4d0c95a5526648749ed99525fc970ce100b0 100644
--- a/cc/tiles/image_controller.h
+++ b/cc/tiles/image_controller.h
@@ -5,11 +5,15 @@
 #ifndef CC_TILES_IMAGE_CONTROLLER_H_
 #define CC_TILES_IMAGE_CONTROLLER_H_
 
+#include <set>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/simple_thread.h"
 #include "cc/base/cc_export.h"
+#include "cc/base/unique_notifier.h"
 #include "cc/playback/draw_image.h"
 #include "cc/raster/tile_task.h"
 #include "cc/tiles/image_decode_cache.h"
@@ -18,8 +22,12 @@ namespace cc {
 
 class CC_EXPORT ImageController {
  public:
-  ImageController();
-  ~ImageController();
+  using ImageDecodeRequestId = uint64_t;
+  using ImageDecodedCallback = base::Callback<void(ImageDecodeRequestId)>;
+  explicit ImageController(
+      base::SequencedTaskRunner* origin_task_runner,
+      scoped_refptr<base::SequencedTaskRunner> worker_task_runner);
+  virtual ~ImageController();
 
   void SetImageDecodeCache(ImageDecodeCache* cache);
   void GetTasksForImagesAndRef(
@@ -32,10 +40,67 @@ class CC_EXPORT ImageController {
       std::vector<DrawImage> predecode_images,
       const ImageDecodeCache::TracingInfo& tracing_info);
 
+  // Virtual for testing.
+  virtual void UnlockImageDecode(ImageDecodeRequestId id);
+
+  // This function requests that the given image be decoded and locked. Once the
+  // callback has been issued, it is passed an ID, which should be used to
+  // unlock this image. It is up to the caller to ensure that the image is later
+  // unlocked using UnlockImageDecode.
+  // Virtual for testing.
+  virtual ImageDecodeRequestId QueueImageDecode(
+      sk_sp<const SkImage> image,
+      const ImageDecodedCallback& callback);
+
  private:
+  struct ImageDecodeRequest {
+    ImageDecodeRequest();
+    ImageDecodeRequest(ImageDecodeRequestId id,
+                       const DrawImage& draw_image,
+                       const ImageDecodedCallback& callback,
+                       scoped_refptr<TileTask> task,
+                       bool need_unref);
+    ImageDecodeRequest(ImageDecodeRequest&& other);
+    ImageDecodeRequest(const ImageDecodeRequest& other);
+    ~ImageDecodeRequest();
+
+    ImageDecodeRequest& operator=(ImageDecodeRequest&& other);
+    ImageDecodeRequest& operator=(const ImageDecodeRequest& other);
+
+    ImageDecodeRequestId id;
+    DrawImage draw_image;
+    ImageDecodedCallback callback;
+    scoped_refptr<TileTask> task;
+    bool need_unref;
+  };
+
+  void ResumeWorkerTasks();
+  void StopWorkerTasks();
+
+  // Called from the worker thread.
+  void ProcessNextImageDecodeOnWorkerThread();
+
+  void ImageDecodeCompleted(ImageDecodeRequestId id);
+
   ImageDecodeCache* cache_ = nullptr;
   std::vector<DrawImage> predecode_locked_images_;
 
+  static ImageDecodeRequestId s_next_image_decode_queue_id_;
+  std::unordered_map<ImageDecodeRequestId, DrawImage> requested_locked_images_;
+
+  base::SequencedTaskRunner* origin_task_runner_ = nullptr;
+  scoped_refptr<base::SequencedTaskRunner> worker_task_runner_;
+
+  // The variables defined below this lock (aside from weak_ptr_factory_) can
+  // only be accessed when the lock is acquired.
+  base::Lock lock_;
+  std::map<ImageDecodeRequestId, ImageDecodeRequest> image_decode_queue_;
+  std::map<ImageDecodeRequestId, ImageDecodeRequest>
+      requests_needing_completion_;
+  bool abort_tasks_ = false;
+
+  base::WeakPtrFactory<ImageController> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ImageController);
 };