ResourceManger11 tracks the total resource count and memoery size.
Such tracking can be concurrently updated from both main thread and
background thread. It can be thread-safe by using std::atomic types
instead.
Also ShaderCache in d3d9 adds a std::mutex to be safe.

Bug: angleproject:2771

Change-Id: Ia7cdcc7fd04579839a5d43e4a02adafb09e6078d
Reviewed-on: https://chromium-review.googlesource.com/1175547Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jie A Chen <jie.a.chen@intel.com>