Revert of Revert of ui:: Add --ui-enable-map-image flag. (https://codereview.chromium.org/198233004/)

Reason for revert:
Reverting the change did not fix the test, so I'm undoing my revert, as scheduled.

Original issue's description:
> Revert of ui:: Add --ui-enable-map-image flag. (https://codereview.chromium.org/199403002/)
> 
> Reason for revert:
> Attempting to see if this fixes a ChromeOS test that has been failing consistently on the ASAN bot since this change was introduced. Will revert the revert if it doesn't fix it.
> 
> http://build.chromium.org/p/chromium.memory/builders/Linux%20Chromium%20OS%20ASan%2BLSan%20Tests%20%281%29/builds/263
> 
> Original issue's description:
> > ui:: Add --ui-enable-map-image flag.
> > 
> > BUG=350737
> > 
> > Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=257020
> 
> TBR=danakj@chromium.org,fjhenigman@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=350737
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=257060

TBR=danakj@chromium.org,fjhenigman@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=350737

Review URL: https://codereview.chromium.org/200193003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257076 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 257076