gpu: Allow overriding GPU driver workarounds via command line

This change allows you to enable GPU driver workarounds by providing command
line switches with the name of the workaround. These workarounds are used
instead of the workarounds loaded from the JSON data. The command line switch
will be propagated into the GPU process allowing these to be applied both with
in-process GPU and without.

BUG=347130
TEST=run content_gl_test or chromium with and without switches and observe
workarounds being applied.

Review URL: https://codereview.chromium.org/180243012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254629 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254629