List gpu driver bug workaround reasons in about:gpu

Before we only list information on why we disable a feature. It helps to also list information on why we apply a driver bug workaround.

BUG=330785
TEST=about:gpu
R=kbr@chromium.org, nduca@chromium.org

Review URL: https://codereview.chromium.org/171453003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252440 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252440