gtk: Make sure TOOLKIT_GTK is defined correctly when not using aura on all x11 platforms.

BUG=342338
R=erg@chromium.org

Review URL: https://codereview.chromium.org/176003002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252952 0039d316-1c4b-4281-b951-d872f2087c98
Remove default browser uma stat.

This metric has been broken since the day it was introduced, over a year
ago, suggesting that nobody cares about it anyway, hence the decision to
remove it rather than fix it.

The actual enum for this is in internal histograms.xml, so that will be
uploaded as a separate review.

BUG=312343
R=isherman@chromium.org

Review URL: https://codereview.chromium.org/175373004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252953 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252953