Added ability to override the number of retries after a browser crash

Set retry count for WebGL conformance tests to zero, because the likelyhood
of flaky crashes being significant are far higher for those tests.

BUG=342881

Review URL: https://codereview.chromium.org/161273002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251612 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251612