cc: Add image decode control in the compositor.

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
index f07892c13f5cc683b2a6df4acb9365c355ccb296..7902b7d7eeb5e4f6bab123dafacbe6f97d8ef3d4 100644
--- a/cc/tiles/image_decode_controller.h
+++ b/cc/tiles/image_decode_controller.h
@@ -6,46 +6,219 @@
 #define CC_TILES_IMAGE_DECODE_CONTROLLER_H_
 
 #include "base/containers/hash_tables.h"
+#include "base/memory/discardable_memory_allocator.h"
 #include "base/memory/ref_counted.h"
+#include "base/numerics/safe_math.h"
+#include "base/threading/thread_checker.h"
 #include "cc/base/cc_export.h"
-#include "cc/playback/discardable_image_map.h"
+#include "cc/playback/decoded_draw_image.h"
+#include "cc/playback/draw_image.h"
 #include "cc/raster/tile_task_runner.h"
 #include "skia/ext/refptr.h"
 
+#include "ui/gfx/transform.h"
+
 namespace cc {
 
-class ImageDecodeController {
+// ImageDecodeControllerKey is a class that gets a cache key out of a given draw
+// image. That is, this key uniquely identifies an image in the cache. Note that
+// it's insufficient to use SkImage's unique id, since the same image can appear
+// in the cache multiple times at different scales and filter qualities.
+class CC_EXPORT ImageDecodeControllerKey {
  public:
+  static ImageDecodeControllerKey FromDrawImage(const DrawImage& image);
+
+  bool operator==(const ImageDecodeControllerKey& other) const {
+    return image_id_ == other.image_id_ && size_ == other.size_ &&
+           filter_quality_ == other.filter_quality_;
+  }
+
+  bool operator!=(const ImageDecodeControllerKey& other) const {
+    return !(*this == other);
+  }
+
+  uint32_t image_id() const { return image_id_; }
+  SkFilterQuality filter_quality() const { return filter_quality_; }
+  gfx::Size target_size() const { return size_; }
+
+  // Helper to figure out how much memory this decoded image would take.
+  size_t target_bytes() const {
+    // TODO(vmpstr): Handle formats other than RGBA.
+    base::CheckedNumeric<size_t> result = 4;
+    result *= size_.width();
+    result *= size_.height();
+    return result.ValueOrDefault(std::numeric_limits<size_t>::max());
+  }
+
+  std::string ToString() const;
+
+ private:
+  ImageDecodeControllerKey(uint32_t image_id,
+                           const gfx::Size& size,
+                           SkFilterQuality filter_quality);
+
+  uint32_t image_id_;
+  gfx::Size size_;
+  SkFilterQuality filter_quality_;
+};
+
+}  // namespace cc
+
+// Hash function for the above ImageDecodeControllerKey.
+namespace BASE_HASH_NAMESPACE {
+template <>
+struct hash<cc::ImageDecodeControllerKey> {
+  size_t operator()(const cc::ImageDecodeControllerKey& key) const {
+    return base::HashPair(
+        static_cast<uint64>(base::HashPair(key.target_size().width(),

[ericrk, 2015/12/04 00:50:46]

nit: prefer uint64_t

+                                           key.target_size().height())),
+        static_cast<uint64>(
+            base::HashPair(key.image_id(), key.filter_quality())));
+  }
+};
+}  // namespace BASE_HASH_NAMESPACE
+
+namespace cc {
+
+// ImageDecodeController is responsible for generating decode tasks, decoding
+// images, storing images in cache, and being able to return the decoded images
+// when requested.
+
+// ImageDecodeController is responsible for the following things:
+// 1. Given a DrawImage, it can return an ImageDecodeTask which when run will
+//    decode and cache the resulting image. If the image does not need a task to
+//    be decoded, then nullptr will be returned. The return value of the
+//    function indicates whether the image was or is going to be locked, so an
+//    unlock will be required.
+// 2. Given a cache key and a DrawImage, it can decode the image and store it in
+//    the cache. Note that it is important that this function is only accessed
+//    via an image decode task.
+// 3. Given a DrawImage, it can return a DecodedDrawImage, which represented the
+//    decoded version of the image. Note that if the image is not in the cache
+//    and it needs to be scaled/decoded, then this decode will happen as part of
+//    getting the image. As such, this should only be accessed from a raster
+//    thread.
+class CC_EXPORT ImageDecodeController {
+ public:
+  using ImageKey = ImageDecodeControllerKey;
+
   ImageDecodeController();
   ~ImageDecodeController();
 
-  scoped_refptr<ImageDecodeTask> GetTaskForImage(const DrawImage& image,
-                                                 int layer_id,
-                                                 uint64_t prepare_tiles_id);
+  // Fill in an ImageDecodeTask which will decode the given image when run. In
+  // case the image is already cached, fills in nullptr. Returns true if the
+  // image needs to be unreffed when the caller is finished with it.
+  //
+  // This is called by the tile manager (on the compositor thread) when creating
+  // a raster task.
+  bool GetTaskForImageAndRef(const DrawImage& image,
+                             uint64_t prepare_tiles_id,
+                             scoped_refptr<ImageDecodeTask>* task);
+  // Unrefs an image. When the tile is finished, this should be called for every
+  // GetTaskForImageAndRef call that returned true.
+  void UnrefImage(const DrawImage& image);
+
+  // Returns a decoded draw image. If the image isn't found in the cache, a
+  // decode will happen.
+  //
+  // This is called by a raster task (on a worker thread) when an image is
+  // required.
+  DecodedDrawImage GetDecodedImageForDraw(const DrawImage& image);
+  // Unrefs an image. This should be called for every GetDecodedImageForDraw
+  // when the draw with the image is finished.
+  void DrawWithImageFinished(const DrawImage& image,
+                             const DecodedDrawImage& decoded_image);
 
-  // Note that this function has to remain thread safe.
-  void DecodeImage(const SkImage* image);
+  // Decode the given image and store it in the cache. This is only called by an
+  // image decode task from a worker thread.
+  void DecodeImage(const ImageKey& key, const DrawImage& image);
 
-  // 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 ReduceCacheUsage();
 
-  void OnImageDecodeTaskCompleted(int layer_id,
-                                  const SkImage* image,
-                                  bool was_canceled);
+  void RemovePendingTask(const ImageKey& key);
+
+  // Info the controller whether we're using gpu rasterization or not. Since the
+  // decode and caching behavior is different for SW and GPU decodes, when the
+  // state changes, we clear all of the caches. This means that this is only
+  // safe to call when there are no pending tasks (and no refs on any images).
+  void SetIsUsingGpuRasterization(bool is_using_gpu_rasterization);
 
  private:
-  scoped_refptr<ImageDecodeTask> CreateTaskForImage(const SkImage* image,
-                                                    int layer_id,
-                                                    uint64_t prepare_tiles_id);
+  // DecodedImage is a convenience storage for discardable memory. It can also
+  // construct an image out of SkImageInfo and stored discardable memory.
+  class DecodedImage : public base::RefCounted<DecodedImage> {
+   public:
+    DecodedImage(const SkImageInfo& info,
+                 scoped_ptr<base::DiscardableMemory> memory);
+
+    SkImage* image() const {
+      DCHECK(locked_);
+      return image_.get();
+    }
+
+    bool is_locked() const { return locked_; }
+    bool Lock();
+    void Unlock();
+
+   private:
+    friend class base::RefCounted<DecodedImage>;
+
+    ~DecodedImage();
+
+    bool locked_;
+    SkImageInfo image_info_;
+    scoped_ptr<base::DiscardableMemory> memory_;
+    skia::RefPtr<SkImage> image_;
+  };
+
+  // MemoryBudget is a convenience class for memory bookkeeping and ensuring
+  // that we don't go over the limit when pre-decoding.
+  class MemoryBudget {

[ericrk, 2015/12/04 00:50:46]

Not as part of this CL :D, but can you add a TODO to add a memory infra logger
for this pool so we can see it's memory usage in dumps.

+   public:
+    explicit MemoryBudget(size_t limit_bytes);
+
+    size_t AvailableMemoryBytes() const;
+    void AddUsage(size_t usage);
+    void SubtractUsage(size_t usage);
+    void ResetUsage();
+
+   private:
+    size_t GetCurrentUsageSafe() const;
+
+    size_t limit_bytes_;
+    base::CheckedNumeric<size_t> current_usage_bytes_;
+  };
+
+  using AnnotatedDecodedImage =
+      std::pair<ImageKey, scoped_refptr<DecodedImage>>;
+
+  // Looks for the key in the cache and returns true if it was found and was
+  // successfully locked (or if it was already locked). Note that if this
+  // function returns true, then a ref count is increased for the image.
+  bool LockDecodedImageIfPossibleAndRef(const ImageKey& key);
+
+  scoped_refptr<DecodedImage> DecodeImageInternal(const ImageKey& key,
+                                                  const SkImage* image);
+  bool CanHandleFilterQuality(SkFilterQuality filter_quality);
+  size_t SanityCheckState(int line, bool lock_acquired);
+  void RefImage(const ImageKey& key);
+  void RefAtRasterImage(const ImageKey& key);
+  void UnrefAtRasterImage(const ImageKey& key);
+  bool ShouldDecodeAndScaleImage(const ImageKey& key, const DrawImage& image);
+
+  bool is_using_gpu_rasterization_;
+  base::hash_map<ImageKey, scoped_refptr<ImageDecodeTask>> pending_image_tasks_;
 
-  using ImageTaskMap = base::hash_map<uint32_t, scoped_refptr<ImageDecodeTask>>;
-  using LayerImageTaskMap = base::hash_map<int, ImageTaskMap>;
-  LayerImageTaskMap image_decode_tasks_;
+  // The members can only be accessed if the lock is held to ensure that they
+  // are safe to access on multiple threads.
+  base::Lock lock_;
+  std::deque<AnnotatedDecodedImage> decoded_images_;
+  base::hash_map<ImageKey, int> decoded_images_ref_counts_;
+  std::deque<AnnotatedDecodedImage> at_raster_decoded_images_;
+  base::hash_map<ImageKey, int> at_raster_decoded_images_ref_counts_;
+  MemoryBudget locked_images_budget_;
 
-  using LayerCountMap = base::hash_map<int, int>;
-  LayerCountMap used_layer_counts_;
+  base::hash_set<uint32_t> prerolled_images_;

[ericrk, 2015/12/04 00:50:46]

does this need to have the lock held? unclear whether the blank line separates
it from the lock-required members above.

 };
 
 }  // namespace cc