Ensure all stats are initialized when calculated Page Load Times
Ensure all stats are initialized when calculated Page Load Times

Some timer values were not initialized before we called to
dump histograms, and this was leading to bogus intervals in 
our stats, and at times, producing DCHECK() failures (for 
overly large values).

BUG=43220
r=davemoore
Review URL: http://codereview.chromium.org/2042007

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@47087 0039d316-1c4b-4281-b951-d872f2087c98

adobe/chromium,adobe/chromium,adobe/chromium,ropik/chromium,adobe/chromium,yitian134/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,adobe/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,yitian134/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,ropik/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,adobe/chromium,yitian134/chromium,adobe/chromium