GitLab

This fixes a regression vs X11 where all touch events are missing
modifier flags.

BUG=450650
TEST=Open http://www.rbyers.net/eventTest.html on link, hold shift, and
     tap the touchscreen. Page shows "shift" on the click event line.

Review URL: https://codereview.chromium.org/887743002

Cr-Commit-Position: refs/heads/master@{#313788}