third_party/angle/src/libANGLE/histogram_macros.h
As of 2016-09-23, the macros defined do a FactoryGet() every time they update a histogram, resulting in the acquisition of a global lock plus a lookup-by-string in a std::map of all histograms known tho the process.

Consider adopting the method in base/metrics/histogram_macros.h and cache a local pointer to the histogram when fetched so that future passes through that macro instantiation can avoid the high lookup cost (90% savings or more).