Update from https://crrev.com/304715

gpu/command_buffer/service/sync_point_manager.cc

+// Copyright (c) 2012 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 "gpu/command_buffer/service/sync_point_manager.h"
+
+#include <climits>
+
+#include "base/logging.h"
+#include "base/rand_util.h"
+
+namespace gpu {
+
+static const int kMaxSyncBase = INT_MAX;
+
+SyncPointManager::SyncPointManager()
+    : next_sync_point_(base::RandInt(1, kMaxSyncBase)) {
+  // To reduce the risk that a sync point created in a previous GPU process
+  // will be in flight in the next GPU process, randomize the starting sync
+  // point number. http://crbug.com/373452
+}
+
+SyncPointManager::~SyncPointManager() {
+}
+
+uint32 SyncPointManager::GenerateSyncPoint() {
+  base::AutoLock lock(lock_);
+  uint32 sync_point = next_sync_point_++;
+  // When an integer overflow occurs, don't return 0.
+  if (!sync_point)
+    sync_point = next_sync_point_++;
+
+  // Note: wrapping would take days for a buggy/compromized renderer that would
+  // insert sync points in a loop, but if that were to happen, better explicitly
+  // crash the GPU process than risk worse.
+  // For normal operation (at most a few per frame), it would take ~a year to
+  // wrap.
+  CHECK(sync_point_map_.find(sync_point) == sync_point_map_.end());
+  sync_point_map_.insert(std::make_pair(sync_point, ClosureList()));
+  return sync_point;
+}
+
+void SyncPointManager::RetireSyncPoint(uint32 sync_point) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  ClosureList list;
+  {
+    base::AutoLock lock(lock_);
+    SyncPointMap::iterator it = sync_point_map_.find(sync_point);
+    if (it == sync_point_map_.end()) {
+      LOG(ERROR) << "Attempted to retire sync point that"
+                    " didn't exist or was already retired.";
+      return;
+    }
+    list.swap(it->second);
+    sync_point_map_.erase(it);
+  }
+  for (ClosureList::iterator i = list.begin(); i != list.end(); ++i)
+    i->Run();
+}
+
+void SyncPointManager::AddSyncPointCallback(uint32 sync_point,
+                                            const base::Closure& callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  {
+    base::AutoLock lock(lock_);
+    SyncPointMap::iterator it = sync_point_map_.find(sync_point);
+    if (it != sync_point_map_.end()) {
+      it->second.push_back(callback);
+      return;
+    }
+  }
+  callback.Run();
+}
+
+bool SyncPointManager::IsSyncPointRetired(uint32 sync_point) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  {
+    base::AutoLock lock(lock_);
+    SyncPointMap::iterator it = sync_point_map_.find(sync_point);
+    return it == sync_point_map_.end();
+  }
+}
+
+}  // namespace gpu