[blimp] Add SkPicture caching support.

blimp/client/feature/compositor/blimp_client_picture_cache.h

Index: blimp/client/feature/compositor/blimp_client_picture_cache.h
diff --git a/blimp/client/feature/compositor/blimp_client_picture_cache.h b/blimp/client/feature/compositor/blimp_client_picture_cache.h
new file mode 100644
index 0000000000000000000000000000000000000000..829fe85d2c8273a2fe22e25ad96c72cee74ee2e2
--- /dev/null
+++ b/blimp/client/feature/compositor/blimp_client_picture_cache.h
@@ -0,0 +1,82 @@
+// Copyright 2016 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 BLIMP_CLIENT_FEATURE_COMPOSITOR_BLIMP_CLIENT_PICTURE_CACHE_H_
+#define BLIMP_CLIENT_FEATURE_COMPOSITOR_BLIMP_CLIENT_PICTURE_CACHE_H_
+
+#include <stdint.h>
+#include <memory>
+#include <unordered_map>
+#include <unordered_set>
+
+#include "base/logging.h"
+#include "base/macros.h"
+#include "blimp/common/compositor/reference_tracker.h"
+#include "cc/proto/picture_cache.h"
+#include "third_party/skia/include/core/SkPicture.h"
+#include "third_party/skia/include/core/SkRefCnt.h"
+
+namespace blimp {
+namespace client {
+
+// BlimpClientPictureCache provides functionality for caching SkPictures once
+// they are received from the engine, and cleaning up once the pictures are no
+// longer in use. It is required to update this cache when an SkPicture starts
+// being used and when it is not longer in use by calling
+// MarkPictureForRegistration and MarkPictureForUnregistration respectively.
+class BlimpClientPictureCache : public cc::ClientPictureCache {

[vmpstr, 2016/06/16 22:09:58]

might need an export

[nyquist, 2016/06/24 11:11:14]

Wouldn't that lead to some kind of compile error or something along those lines
if I needed it?

+ public:
+  explicit BlimpClientPictureCache(
+      SkPicture::InstallPixelRefProc pixel_deserializer);
+  ~BlimpClientPictureCache() override;
+
+  // cc::ClientPictureCache implementation.
+  sk_sp<const SkPicture> GetPicture(uint32_t engine_picture_id) override;
+  void ApplyCacheUpdate(const cc::PictureCacheUpdate& cache_update) override;
+  void Flush() override;
+  void MarkPictureForUnregistration(uint32_t engine_picture_id) override;
+  void MarkPictureForRegistration(uint32_t engine_picture_id) override;
+
+ private:
+  // Adds new pictures from the |cache_update| to |pictures_|.
+  void AddNewPicturesToCache(const cc::PictureCacheUpdate& cache_update);
+
+  // Removes all unusued pictures from |pictures_|.
+  void RemoveUnusedPicturesFromCache(const std::vector<uint32_t>& picture_ids);

[vmpstr, 2016/06/16 22:09:58]

comment on what the parameter is

[nyquist, 2016/06/24 11:11:14]

Done.

+
+  // Retrieves the SkPicture with the given |picture_id| from the cache. The
+  // given |picture_id| is the unique ID that the engine used to identify the
+  // picture in the cc::PictureCacheUpdate that contained the image.
+  sk_sp<const SkPicture> GetPictureFromCache(uint32_t picture_id);
+
+#if DCHECK_IS_ON()
+  // Verify that the incoming cache update matches the new items that were added
+  // to the |reference_tracker_|.
+  void VerifyCacheUpdateMatchesReferenceTrackerData(
+      const std::vector<uint32_t>& new_tracked_items);
+
+  // A set of the items that were added when the last cache update was applied.
+  // Used for verifying that the calculation from the registry matches the
+  // expectations.
+  std::unordered_set<uint32_t> last_added_;
+#endif  // DCHECK_IS_ON()
+
+  // A function pointer valid to use for deserializing images when
+  // using SkPicture::CreateFromStream to create an SkPicture from a stream.
+  SkPicture::InstallPixelRefProc pixel_deserializer_;
+
+  // The current cache of SkPictures. The key is the unique ID used by the
+  // engine, and the value is the SkPicture itself.
+  std::unordered_map<uint32_t, sk_sp<const SkPicture>> pictures_;
+
+  // The reference tracker maintains the reference count of used SkPictures.
+  ReferenceTracker reference_tracker_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlimpClientPictureCache);
+};
+
+}  // namespace client
+}  // namespace blimp
+
+#endif  // BLIMP_CLIENT_FEATURE_COMPOSITOR_BLIMP_CLIENT_PICTURE_CACHE_H_