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* Remove touch drag for a series of tests about tab dragging to the second display as, up to now, there's no use case.

* Each display has its own UI controller in the test, but, in ozone build, they do not share the state of mouse (down, up). When the mouse is moved to the second display, the UI controller for it does know that the mouse is down in first display. That's why the tab cannot be dragged to the second display only in ozone build. Simple solution is to move the mouse state variable outside of UI controller class.

BUG=626769

Review-Url: https://codereview.chromium.org/2836073003
Cr-Commit-Position: refs/heads/master@{#468048}