GitLab

Redirect all mouse input to Alt+Tab window when it's visible,
effectively disabling the mouse. Capture is reset when the widget is
destroyed.

original review: https://codereview.chromium.org/2284763002/

BUG=641171

Review-Url: https://codereview.chromium.org/2296763002
Cr-Commit-Position: refs/heads/master@{#415761}