Support uploading error images to cloud storage directly in Maps test.

This completes the refactoring of the pixel and maps tests, for the time
being. The naming convention of the on-disk error image for the Maps test
is changed to use the FAIL_ prefix to be more clear, since the
archive_gpu_pixel_test_results.py script will not be used anymore when
uploading to cloud storage.

Tested pixel and maps tests, both using on-disk storage and cloud storage,
and both passing and failing scenarios. All are working as expected.

Once this lands, the GPU recipe will be updated right away to switch the
Maps test to use cloud storage, and remove the archive_pixel_test_results
step entirely.

BUG=330774
TBR=bajones@chromium.org

Review URL: https://codereview.chromium.org/112163007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242651 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242651