Revert 255091 "linux_aura: Fix all instances of LabelButton sizing."

Patch is incorrect. Changing the behaviour of insets also breaks the
toolbar. Looks like I'm going to have to find all usage of
LabelButton::set_min_size() after all.

> linux_aura: Fix all instances of LabelButton sizing.
> 
> Previous attempts at fixing this involved tracking down each button
> which was setting the minimum size to 0,0. Those attempts are reverted,
> as I no longer think they're wrong. The actual fix is to pass through
> the views inset size instead of using the GTK inset size.
> 
> BUG=349183, 344498, 339247
> R=msw@chromium.org, sky@chromium.org
> 
> Review URL: https://codereview.chromium.org/187133003

TBR=erg@chromium.org,msw@chromium.org,sky@chromium.org
BUG=349777

Review URL: https://codereview.chromium.org/188893003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255406 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255406