[blimp] Add SkPicture caching support.

cc/blimp/client_picture_cache.h

+// 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 CC_BLIMP_CLIENT_PICTURE_CACHE_H_
+#define CC_BLIMP_CLIENT_PICTURE_CACHE_H_
+
+#include <vector>
+
+#include "third_party/skia/include/core/SkRefCnt.h"
+
+class SkPicture;
+
+namespace cc {
+struct PictureData;
+
+// ClientPictureCache provides functionaltiy for marking when SkPictures are in
+// use an when they stop being in use. PictureCacheUpdates are provided
+// with all new SkPictures that a client needs and the respective unique IDs
+// used on the engine. The SkPictures are kept in memory until they are no
+// longer in use.
+class ClientPictureCache {
+ public:
+  virtual ~ClientPictureCache() {}
+
+  // MarkUsed must be called when the client has started using an SkPicture that
+  // was sent to from the engine.
+  virtual void MarkUsed(uint32_t engine_picture_id) = 0;
+
+  // Retrieves an SkPicture from the in-memory cache. It is required that the
+  // provided ID is the same as the unique ID that is given through the cache
+  // update.
+  virtual sk_sp<const SkPicture> GetPicture(uint32_t engine_picture_id) = 0;
+
+  // Called when a PictureCacheUpdate has been retrieved from the engine. This
+  // must contain all the new SkPictures that are in use.
+  virtual void ApplyCacheUpdate(const std::vector<PictureData>& pictures) = 0;
+
+  // Flushes the current state of the cache, removing unused SkPictures. Must be
+  // called after deserialization is finished.
+  virtual void Flush() = 0;
+};
+
+}  // namespace cc
+
+#endif  // CC_BLIMP_CLIENT_PICTURE_CACHE_H_