Fix crash caused by concurrent access to framebuffer_combo_complete_map_.

gpu/command_buffer/service/framebuffer_completeness_cache.cc

+// Copyright 2015 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/framebuffer_completeness_cache.h"
+
+namespace gpu {
+namespace gles2 {
+
+FramebufferCompletenessCache::FramebufferCompletenessCache() {}
+
+FramebufferCompletenessCache::~FramebufferCompletenessCache() {}
+
+bool FramebufferCompletenessCache::IsComplete(
+    const std::string& signature) const {
+  return cache_.find(signature) != cache_.end();
+}
+
+void FramebufferCompletenessCache::SetComplete(const std::string& signature) {
+  cache_.insert(signature);
+}
+
+}  // namespace gles2
+}  // namespace gpu