GitLab

Adds touch feedback to tray icons in touchview when --ash-enable-touchview-touch-feedback flag is passed.

TEST=WebNotificationTrayTest.MAYBE_NoTouchFeedback, WebNotificationTrayTest.MAYBE_MaximizeModeTouchFeedback, WebNotificationTrayTest.MAYBE_TouchFeedbackCancellation
BUG=398398

Review URL: https://codereview.chromium.org/515573002

Cr-Commit-Position: refs/heads/master@{#293608}