fix bug to not show context menu when mouse is between tabstrip and toolbar.
fix bug to not show context menu when mouse is between tabstrip and toolbar.

BUG=33454
TEST=verify per bug report.

Review URL: http://codereview.chromium.org/650071

git-svn-id: http://src.chromium.org/svn/trunk/src@39501 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 3f0e6ac6b6423b688212836cd9dcac83511256f2
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser