Instrument NaCl validation caching with UMA histograms.
Instrument NaCl validation caching with UMA histograms.

BUG= http://code.google.com/p/nativeclient/issues/detail?id=2515
TEST= Run NaCl w/ NACL_VALIDATION_CACHE=1


Review URL: http://codereview.chromium.org/9866011

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@129113 0039d316-1c4b-4281-b951-d872f2087c98

gavinp/chromium,yitian134/chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,ropik/chromium,yitian134/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,ropik/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,gavinp/chromium,gavinp/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,ropik/chromium,ropik/chromium,adobe/chromium,adobe/chromium,ropik/chromium,gavinp/chromium,yitian134/chromium,adobe/chromium,yitian134/chromium,adobe/chromium