GTK: Implement OnDragCanceled() for autocomplete popup view on linux.

Pressing escape while performing a drag inside the autocomplete popup should
abort the drag and not changed the selected item. This is a rewrite of
pkasting's r37724 for GTK instead of views.

BUG=35710
TEST=none

Review URL: http://codereview.chromium.org/1758002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@45322 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed