cc: Move image decodes from tile manager to a separate file.

cc/tiles/image_decode_controller.h

Index: cc/tiles/image_decode_controller.h
diff --git a/cc/tiles/image_decode_controller.h b/cc/tiles/image_decode_controller.h
new file mode 100644
index 0000000000000000000000000000000000000000..9f9090663df95767c7e89eb151d3d03f6eceda33
--- /dev/null
+++ b/cc/tiles/image_decode_controller.h
@@ -0,0 +1,55 @@
+// Copyright 2015 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_IMAGE_DECODE_CONTROLLER_H_
+#define CC_TILES_IMAGE_DECODE_CONTROLLER_H_
+
+#include "base/containers/hash_tables.h"
+#include "base/memory/ref_counted.h"
+#include "cc/base/cc_export.h"
+#include "cc/raster/tile_task_runner.h"
+#include "skia/ext/refptr.h"
+#include "third_party/skia/include/core/SkPixelRef.h"
+
+namespace cc {
+
+class CC_EXPORT ImageDecodeController {

[ericrk, 2015/07/30 22:59:30]

does this need CC_EXPORT as it seems to be only used by tile_manager?

[vmpstr, 2015/07/30 23:08:34]

Removed. We'll probably be unittesting this as well :P so I'll re-add it when we
actually need it. 

+ public:
+  ImageDecodeController();
+  ~ImageDecodeController();
+
+  scoped_refptr<ImageDecodeTask> GetTaskForPixelRef(SkPixelRef* pixel_ref,
+                                                    int layer_id,
+                                                    uint64_t prepare_tiles_id);
+
+  // Note that this function has to remain thread safe.
+  void DecodePixelRef(SkPixelRef* pixel_ref) const;

[ericrk, 2015/07/30 22:59:30]

nit: maybe it's the same difference, but should this just be static rather than
const? doesn't refer to any class state. - I guess it could though, so if you're
leaving it open to that, sounds good.

[vmpstr, 2015/07/30 23:08:34]

Eventually the goal is to make this act like a cache with DecodePixelRef storing
results for future use. So I actually removed const from this as well to leave
the decision of what to do in this function up to the controller.

+
+  // TODO(vmpstr): This should go away once the controller is decoding images
+  // based on priority and memory.
+  void AddLayerUsedCount(int layer_id);
+  void SubtractLayerUsedCount(int layer_id);
+
+  void OnImageDecodeTaskCompleted(int layer_id,
+                                  SkPixelRef* pixel_ref,
+                                  bool was_canceled);
+
+ private:
+  scoped_refptr<ImageDecodeTask> CreateTaskForPixelRef(
+      SkPixelRef* pixel_ref,
+      int layer_id,
+      uint64_t prepare_tiles_id);
+
+  using PixelRefTaskMap =
+      base::hash_map<uint32_t, scoped_refptr<ImageDecodeTask>>;
+  using LayerPixelRefTaskMap = base::hash_map<int, PixelRefTaskMap>;
+  LayerPixelRefTaskMap image_decode_tasks_;
+
+  using LayerCountMap = base::hash_map<int, int>;
+  LayerCountMap used_layer_counts_;
+};
+
+}  // namespace cc
+
+#endif  // CC_TILES_IMAGE_DECODE_CONTROLLER_H_