Added method to synchronize command buffers within GpuControl.

gpu/command_buffer/tests/gl_manager.cc

Index: gpu/command_buffer/tests/gl_manager.cc
diff --git a/gpu/command_buffer/tests/gl_manager.cc b/gpu/command_buffer/tests/gl_manager.cc
index 9ad141e2b216a6ce4e9f7e356acd03a3d0c696e0..c787746549e6143ba5fef23fe8c73af83cb34daf 100644
--- a/gpu/command_buffer/tests/gl_manager.cc
+++ b/gpu/command_buffer/tests/gl_manager.cc
@@ -499,6 +499,10 @@ bool GLManager::IsGpuChannelLost() {
   return false;
 }
 
+void GLManager::SynchronizeCommandBuffer() {
+  // This is only relevant for out-of-process command buffers.
+}
+
 gpu::CommandBufferNamespace GLManager::GetNamespaceID() const {
   return gpu::CommandBufferNamespace::IN_PROCESS;
 }