[blimp] Add SkPicture caching support.

blimp/client/feature/compositor/blimp_client_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/client/feature/compositor/blimp_client_picture_cache.h"
+
+#include <stdint.h>
+#include <map>
+#include <memory>
+
+#include "base/logging.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/SkRefCnt.h"
+#include "third_party/skia/include/core/SkStream.h"
+
+namespace blimp {
+namespace client {
+
+BlimpClientPictureCache::BlimpClientPictureCache(
+    SkPicture::InstallPixelRefProc pixel_deserializer)
+    : pixel_deserializer_(pixel_deserializer) {}
+
+BlimpClientPictureCache::~BlimpClientPictureCache() {}
+
+sk_sp<const SkPicture> BlimpClientPictureCache::GetPicture(
+    uint32_t engine_picture_id) {
+  if (pictures_.find(engine_picture_id) == pictures_.end()) {
+    NOTREACHED() << "Failed to find picture with id = " << engine_picture_id;

[vmpstr, 2016/05/25 01:54:05]

Remind me what the policy on error handling is? In normal chromium code, this
would be a DCHECK(pictures_.find(engine_picture_id) != pictures_.end()); Why
isn't it that here?

[nyquist, 2016/05/26 01:08:09]

Done.

+    return nullptr;
+  }
+
+  return pictures_.find(engine_picture_id)->second;
+}
+
+void BlimpClientPictureCache::ApplyCacheUpdate(
+    const cc::PictureCacheUpdate& cache_update) {
+  for (const cc::PictureData& picture_data : cache_update) {
+    sk_sp<SkPicture> deserialized_picture = DeserializePicture(picture_data);
+    DCHECK(pictures_.find(picture_data.unique_id) == pictures_.end());
+    pictures_.insert(
+        std::make_pair(picture_data.unique_id, deserialized_picture));

[vmpstr, 2016/05/25 01:54:05]

How does unique_id related to SkPicture::uniqueID()?

[nyquist, 2016/05/26 01:08:09]

It's the SkPicture::uniqueID() that the engine used, so we can't use the
deserialized_picture->uniqueID(). Do you think we should name the field
engine_unique_id or something like that instead?

+    last_added_.insert(picture_data.unique_id);
+  }
+}
+
+void BlimpClientPictureCache::Flush() {
+  std::set<uint32_t> added;
+  std::set<uint32_t> removed;
+  registry_.Commit(&added, &removed);
+
+  // Verify that the incoming cache update matches the new items.
+  DCHECK(added == last_added_);
+  last_added_.clear();
+
+  for (const auto& it : removed) {
+    auto entry = pictures_.find(it);
+    if (entry == pictures_.end()) {
+      NOTREACHED() << "PictureMap does not contain entry " << it;
+      continue;
+    }
+    pictures_.erase(entry);
+  }
+}
+
+sk_sp<SkPicture> BlimpClientPictureCache::DeserializePicture(
+    const cc::PictureData& picture_data) {
+  SkMemoryStream stream(picture_data.data);
+  return SkPicture::MakeFromStream(&stream, pixel_deserializer_);
+}
+
+void BlimpClientPictureCache::MarkPictureForUnregistration(
+    uint32_t engine_picture_id) {
+  registry_.Unstage(engine_picture_id);

[vmpstr, 2016/05/25 01:54:05]

Technically this is stage for removal, not unstage... Unstage would imply to
undo a staging done by Mark function below. I'm not too picky on the names
though.

[nyquist, 2016/05/26 01:08:09]

Done.

+}
+
+void BlimpClientPictureCache::MarkPictureForRegistration(
+    uint32_t engine_picture_id) {
+  registry_.Stage(engine_picture_id);
+}
+
+}  // namespace client
+}  // namespace blimp