Fix crash caused by concurrent access to framebuffer_combo_complete_map_.

content/common/gpu/gpu_channel_manager.cc

Index: content/common/gpu/gpu_channel_manager.cc
diff --git a/content/common/gpu/gpu_channel_manager.cc b/content/common/gpu/gpu_channel_manager.cc
index 040deb92beff8b5c7ebf986118d383d6d673dda1..21672e295b9618ca4e7ae357bade7c17814cfda2 100644
--- a/content/common/gpu/gpu_channel_manager.cc
+++ b/content/common/gpu/gpu_channel_manager.cc
@@ -79,6 +79,14 @@ GpuChannelManager::shader_translator_cache() {
   return shader_translator_cache_.get();
 }
 
+gpu::gles2::FramebufferCompletenessCache*
+GpuChannelManager::framebuffer_completeness_cache() {
+  if (!framebuffer_completeness_cache_.get())
+    framebuffer_completeness_cache_ =
+        new gpu::gles2::FramebufferCompletenessCache;
+  return framebuffer_completeness_cache_.get();
+}
+
 void GpuChannelManager::RemoveChannel(int client_id) {
   Send(new GpuHostMsg_DestroyChannel(client_id));
   gpu_channels_.erase(client_id);