Fix histogram perf result processing.
Fix histogram perf result processing.

The histogram doesn't have a count, each bucket does. See bug for full
explanation.

BUG=404251

Review URL: https://codereview.chromium.org/508423002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@291702 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build