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 1e8a4f6e1d1132efeff343cbdd5fcb5aa32b7078..a27306ca3a3cfbbe2cb6aa39bd442ce2378e2208 100644
--- a/mojo/services/gles2/command_buffer_impl.cc
+++ b/mojo/services/gles2/command_buffer_impl.cc
@@ -96,6 +96,7 @@ bool CommandBufferImpl::DoInitialize(const ShmHandle& shared_state) {
   std::vector<int32> attrib_vector;
   if (!decoder_->Initialize(surface,
                             context,
+                            new gpu::gles2::ShaderTranslatorCache,

[no sievers, 2014/04/02 18:30:19]

We don't actually have to create one per decoder, but can at least store it in
the ContextGroup, or even better maybe ShaderManager (owned by ContextGroup).

piman@ might further know if there is a good place for mojo to share this more
widely, in case creation cost in terms of time and memory for the translator is
still an issue nowadays.

[piman, 2014/04/02 21:58:33]

Currently, mojo support is still in its infancy. We don't support ContextGroups
yet (see TODOs above).
It's fine to create one per ContextGroup in mojo for now, just add a TODO(piman)
about it only needing to be per-thread?

                             false /* offscreen */,
                             size_,
                             disallowed_features,