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The stylus tools would be shown previous when adding a supervised user. They could also be shown by ejecting the stylus at any point.

This CL also causes the active mode to turn off when the user inserts the stylus.

BUG=647025

Review-Url: https://codereview.chromium.org/2346833003
Cr-Commit-Position: refs/heads/master@{#419278}