Fix a few issues with the drop arrow in the Linux tab strip:...

Fix a few issues with the drop arrow in the Linux tab strip:
* Reset the drop info when completing a drag (successful or otherwise).
* Reset the drop info when the drag leaves the tab strip zone.
* Report success or failure of the drop back to the source widget.
* Move and resize the drop arrow container before showing it to reduce visual jank.

BUG=none
TEST=Drag a image into the tab strip so that the drop arrow appears.  Release the drop over the tab strip and then move the window and repeat the process.  The drop arrow should be in the correct position.  Notice that there is no visual jank when the drop arrow is shown.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=20404

[tony, 2009-07-10 00:49:09]

LGTM