[blimp] Add SkPicture caching support.

blimp/engine/renderer/blimp_engine_picture_cache.cc

+// 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.
+
+#include "blimp/engine/renderer/blimp_engine_picture_cache.h"
+
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "third_party/skia/include/core/SkStream.h"
+
+namespace blimp {
+namespace engine {
+
+BlimpEnginePictureCache::BlimpEnginePictureCache(
+    SkPixelSerializer* pixel_serializer)
+    : pixel_serializer_(pixel_serializer) {}
+
+BlimpEnginePictureCache::~BlimpEnginePictureCache() = default;
+
+void BlimpEnginePictureCache::MarkUsed(const SkPicture* picture) {
+  DCHECK(picture);
+  reference_tracker_.IncrementRefCount(picture->uniqueID());
+
+  // Do not serialize multiple times, even though the item is referred to from
+  // multiple places.
+  if (pictures_.find(picture->uniqueID()) != pictures_.end()) {
+    return;
+  }
+
+  Put(picture);
+}
+
+std::vector<cc::PictureData>
+BlimpEnginePictureCache::CalculateCacheUpdateAndFlush() {
+  std::vector<uint32_t> added;
+  std::vector<uint32_t> removed;
+  reference_tracker_.CommitRefCounts(&added, &removed);
+
+  // Create cache update consisting of new pictures.
+  std::vector<cc::PictureData> update;
+  for (const uint32_t item : added) {
+    auto entry = pictures_.find(item);
+    DCHECK(entry != pictures_.end());
+    update.push_back(entry->second);
+  }
+
+  // All new items will be sent to the client, so clear everything.
+  pictures_.clear();
+  reference_tracker_.ClearRefCounts();
+
+  return update;
+}
+
+void BlimpEnginePictureCache::Put(const SkPicture* picture) {
+  SkDynamicMemoryWStream stream;
+  picture->serialize(&stream, pixel_serializer_);
+  DCHECK_GE(stream.bytesWritten(), 0u);
+
+  // Store the picture data until it is sent to the client.
+  pictures_.insert(
+      std::make_pair(picture->uniqueID(),
+                     cc::PictureData(picture->uniqueID(),
+                                     sk_sp<SkData>(stream.copyToData()))));
+}
+
+}  // namespace engine
+}  // namespace blimp