src

Corruptions can include changes in bucket boundaries,
large changes in sample counts (in a bucket), etc.

We now detect problems, and don't forward the corrupt
data any further. This means it won't exit the renderer
and go to the browser if corrupt, and it won't exit
the browser and be sent up via UMA if corrupt.

IF the would-be corruption is caused by a race to
snapshot the data, then a later snapshot should get
the clean copy, and all data (across the precluded
period) will be sent onward.

BUG=61281
r=mbelshe
Review URL: http://codereview.chromium.org/4174002

TBR=jar@chromium.org
Review URL: http://codereview.chromium.org/4349002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@64846 0039d316-1c4b-4281-b951-d872f2087c98