Added a unique command buffer ID for command buffers.

mojo/gles2/command_buffer_client_impl.cc

Index: mojo/gles2/command_buffer_client_impl.cc
diff --git a/mojo/gles2/command_buffer_client_impl.cc b/mojo/gles2/command_buffer_client_impl.cc
index b639f6e40472b2337f4fc5f3ec5040ea992ec3b7..f92f47e5588f1acb78a9d6b54ae65a9e863b7be2 100644
--- a/mojo/gles2/command_buffer_client_impl.cc
+++ b/mojo/gles2/command_buffer_client_impl.cc
@@ -393,4 +393,13 @@ bool CommandBufferClientImpl::IsGpuChannelLost() {
   return false;
 }
 
+gpu::CommandBufferNamespace CommandBufferClientImpl::GetNamespaceID() const {
+  return gpu::kCommandBufferNamespace_Mojo;
+}
+
+uint64_t CommandBufferClientImpl::GetCommandBufferID() const {
+  NOTIMPLEMENTED();
+  return 0;
+}
+
 }  // namespace gles2