Make ShaderTranslatorCache thread safe

mojo/services/gles2/command_buffer_impl.cc

Index: mojo/services/gles2/command_buffer_impl.cc
diff --git a/mojo/services/gles2/command_buffer_impl.cc b/mojo/services/gles2/command_buffer_impl.cc
index 7d33b722cd8ddb24fc0fab5e4a392fa0b4698643..7a546b60986597a4f7d848cb680d76ace276f7ad 100644
--- a/mojo/services/gles2/command_buffer_impl.cc
+++ b/mojo/services/gles2/command_buffer_impl.cc
@@ -77,9 +77,16 @@ bool CommandBufferImpl::DoInitialize(const ShmHandle& shared_state) {
   if (!context->MakeCurrent(surface.get()))
     return false;
 
+  // TODO(piman): ShaderTranslatorCache is currently per-ContextGroup but
+  // only needs to be per-thread.
   scoped_refptr<gpu::gles2::ContextGroup> context_group =
-      new gpu::gles2::ContextGroup(
-          NULL, NULL, new MemoryTrackerStub(), NULL, true);
+      new gpu::gles2::ContextGroup(NULL,
+                                   NULL,
+                                   new MemoryTrackerStub,
+                                   new gpu::gles2::ShaderTranslatorCache,
+                                   NULL,
+                                   true);
+
   command_buffer_.reset(
       new gpu::CommandBufferService(context_group->transfer_buffer_manager()));
   bool result = command_buffer_->Initialize();