[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 <memory>
+#include <sstream>
+#include <unordered_map>
+#include <vector>
+
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "blimp/common/compositor/blimp_picture_cache_registry.h"
+#include "cc/proto/picture_cache.h"
+#include "third_party/skia/include/core/SkPicture.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::MarkPictureForUnregistration(
+    const SkPicture* picture) {
+  registry_.DecrementRefCount(picture->uniqueID());
+}
+
+void BlimpEnginePictureCache::MarkPictureForRegistration(
+    const SkPicture* picture) {
+  registry_.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;
+  }
+
+  // Use skia's serialize() method for now.

[Kevin M, 2016/06/06 23:33:59]

For now... until what? Got more detail or a bug?

[nyquist, 2016/06/10 22:02:24]

Well, we have in fact kind of settled for this until we change it, so this
comment seems unnecessary now. Removed.

+  SkDynamicMemoryWStream stream;
+  picture->serialize(&stream, pixel_serializer_);
+  DCHECK_GE(stream.bytesWritten(), 0u);
+
+  // Store the picture data until it is sent to the client.
+  cc::PictureData picture_data;
+  picture_data.unique_id = picture->uniqueID();
+  picture_data.data.reset(stream.copyToData());
+  pictures_[picture_data.unique_id] = picture_data;
+}
+
+cc::PictureCacheUpdate BlimpEnginePictureCache::CalculateCacheUpdateAndFlush() {
+  std::vector<uint32_t> added;
+  std::vector<uint32_t> removed;
+  registry_.Commit(&added, &removed);
+
+  // Create cache update consisting of new pictures.
+  cc::PictureCacheUpdate update;
+  for (const auto it : added) {

[Kevin M, 2016/06/06 23:33:59]

"it" - good name for an iterator, not so good for a value

[nyquist, 2016/06/10 22:02:24]

Done.

+    auto entry = pictures_.find(it);
+    if (entry == pictures_.end()) {
+      NOTREACHED() << "Picture map does not contain entry " << it;

[Kevin M, 2016/06/06 23:33:59]

This is more like a DLOG(ERROR). NOTREACHED() means it's an impossible code
path, but this is reachable by -a bug or a data error.

[nyquist, 2016/06/10 22:02:24]

Done. Thanks for the clarification!

+      continue;
+    }
+    update.push_back(entry->second);
+  }
+
+  // All new items will be sent to client, so clear everything.
+  pictures_.clear();
+
+  return update;
+}
+
+}  // namespace engine
+}  // namespace blimp