Allow ui_tests to be run in parallel
Allow ui_tests to be run in parallel

Added an environment variable for CHROME_LOG_FILE

TEST=ui_tests pass when run with sharding_supervisor


Review URL: http://codereview.chromium.org/7554013

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@95152 0039d316-1c4b-4281-b951-d872f2087c98

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