[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 <sstream>
+
+#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)

[Kevin M, 2016/06/11 00:29:33]

DCHECK(pixel_serializer)

[nyquist, 2016/06/14 01:37:57]

A nullptr pixel serializer ends up using the default one in Skia, so a nullptr
is in fact valid. So keeping as is unless you feel strongly.

+    : pixel_serializer_(pixel_serializer) {}
+
+BlimpEnginePictureCache::~BlimpEnginePictureCache() = default;
+
+void BlimpEnginePictureCache::MarkPictureForUnregistration(
+    const SkPicture* picture) {

[Kevin M, 2016/06/11 00:29:32]

DCHECK(picture)

[nyquist, 2016/06/14 01:37:57]

Done.

+  reference_tracker_.DecrementRefCount(picture->uniqueID());
+}
+
+void BlimpEnginePictureCache::MarkPictureForRegistration(
+    const SkPicture* picture) {

[Kevin M, 2016/06/11 00:29:33]

DCHECK(picture)

[nyquist, 2016/06/14 01:37:57]

Done.

+  reference_tracker_.IncrementRefCount(picture->uniqueID());
+
+  // Do not serialize multiple times, even though the item is referred to from
+  // multiple places.
+  if (CacheContainsPicture(picture)) {
+    return;
+  }
+
+  SerializePictureAndAddToCache(picture);
+}
+
+cc::PictureCacheUpdate BlimpEnginePictureCache::CalculateCacheUpdateAndFlush() {
+  std::vector<uint32_t> added;
+  std::vector<uint32_t> removed;
+  reference_tracker_.CommitRefCounts(&added, &removed);
+
+  // Create cache update consisting of new pictures.
+  cc::PictureCacheUpdate update;
+  for (const uint32_t item : added) {
+    auto entry = pictures_.find(item);
+    if (entry == pictures_.end()) {
+      DLOG(ERROR) << "Picture map does not contain item " << item;

[Kevin M, 2016/06/11 00:29:33]

How messed up is it if this happens? If the answer is "very", how about
DCHECKing?

[nyquist, 2016/06/14 01:37:57]

Pretty messed up. 
Done.

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

[Kevin M, 2016/06/11 00:29:32]

the client

[nyquist, 2016/06/14 01:37:57]

Done.

+  pictures_.clear();
+
+  return update;
+}
+
+bool BlimpEnginePictureCache::CacheContainsPicture(const SkPicture* picture) {
+  return pictures_.find(picture->uniqueID()) != pictures_.end();
+}
+
+void BlimpEnginePictureCache::SerializePictureAndAddToCache(
+    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.
+  cc::PictureData picture_data;
+  picture_data.unique_id = picture->uniqueID();
+  picture_data.data.reset(stream.copyToData());
+  pictures_[picture_data.unique_id] = picture_data;
+}
+
+}  // namespace engine
+}  // namespace blimp