[blimp] Add SkPicture caching support.

blimp/client/feature/compositor/blimp_client_picture_cache.cc

Index: blimp/client/feature/compositor/blimp_client_picture_cache.cc
diff --git a/blimp/client/feature/compositor/blimp_client_picture_cache.cc b/blimp/client/feature/compositor/blimp_client_picture_cache.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b751e50b5a0faa64d125d7696b77ddbd9c73ea5e
--- /dev/null
+++ b/blimp/client/feature/compositor/blimp_client_picture_cache.cc
@@ -0,0 +1,98 @@
+// 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/client/feature/compositor/blimp_client_picture_cache.h"
+
+#include <utility>
+#include <vector>
+
+#include "third_party/skia/include/core/SkStream.h"
+
+namespace blimp {
+namespace client {
+namespace {
+
+// Helper function to deserialize the content of |picture_data| into an
+// SkPicture.
+sk_sp<const SkPicture> DeserializePicture(
+    SkPicture::InstallPixelRefProc pixel_deserializer,
+    const cc::PictureData& picture_data) {
+  SkMemoryStream stream(picture_data.data);
+  return SkPicture::MakeFromStream(&stream, pixel_deserializer);
+}
+
+}  // namespace
+
+BlimpClientPictureCache::BlimpClientPictureCache(
+    SkPicture::InstallPixelRefProc pixel_deserializer)
+    : pixel_deserializer_(pixel_deserializer) {}
+
+BlimpClientPictureCache::~BlimpClientPictureCache() = default;
+
+sk_sp<const SkPicture> BlimpClientPictureCache::GetPicture(
+    uint32_t engine_picture_id) {
+  return GetPictureFromCache(engine_picture_id);
+}
+
+void BlimpClientPictureCache::ApplyCacheUpdate(
+    const std::vector<cc::PictureData>& cache_update) {
+  // Add new pictures from the |cache_update| to |pictures_|.
+  for (const cc::PictureData& picture_data : cache_update) {
+    DCHECK(pictures_.find(picture_data.unique_id) == pictures_.end());
+    sk_sp<const SkPicture> deserialized_picture =
+        DeserializePicture(pixel_deserializer_, picture_data);
+
+    pictures_[picture_data.unique_id] = std::move(deserialized_picture);
+
+#if DCHECK_IS_ON()
+    last_added_.insert(picture_data.unique_id);
+#endif  // DCHECK_IS_ON()
+  }
+}
+
+void BlimpClientPictureCache::Flush() {
+  // Calculate which pictures can now be removed. |added| is only used for
+  // verifying that what we calculated matches the new items that have been
+  // inserted into the cache.
+  std::vector<uint32_t> added;
+  std::vector<uint32_t> removed;
+  reference_tracker_.CommitRefCounts(&added, &removed);
+
+  VerifyCacheUpdateMatchesReferenceTrackerData(added);
+
+  RemoveUnusedPicturesFromCache(removed);
+  reference_tracker_.ClearRefCounts();
+}
+
+void BlimpClientPictureCache::MarkUsed(uint32_t engine_picture_id) {
+  reference_tracker_.IncrementRefCount(engine_picture_id);
+}
+
+void BlimpClientPictureCache::RemoveUnusedPicturesFromCache(
+    const std::vector<uint32_t>& removed) {
+  for (const auto& engine_picture_id : removed) {
+    auto entry = pictures_.find(engine_picture_id);
+    DCHECK(entry != pictures_.end());
+    pictures_.erase(entry);
+  }
+}
+
+sk_sp<const SkPicture> BlimpClientPictureCache::GetPictureFromCache(
+    uint32_t engine_picture_id) {
+  DCHECK(pictures_.find(engine_picture_id) != pictures_.end());
+  return pictures_[engine_picture_id];
+}
+
+void BlimpClientPictureCache::VerifyCacheUpdateMatchesReferenceTrackerData(
+    const std::vector<uint32_t>& new_tracked_items) {
+#if DCHECK_IS_ON()
+  DCHECK_EQ(new_tracked_items.size(), last_added_.size());
+  DCHECK(std::unordered_set<uint32_t>(new_tracked_items.begin(),
+                                      new_tracked_items.end()) == last_added_);
+  last_added_.clear();
+#endif  // DCHECK_IS_ON()
+}
+
+}  // namespace client
+}  // namespace blimp