gtk: Use the requested window bounds when determining the location of the source tab.  This is necessary because we move the hidden source tab during a drag, and gtk does not update the allocation of hidden widgets.

BUG=16918,17712
TEST=Extensive tab dragging.
Review URL: http://codereview.chromium.org/159436

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@21729 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed