[DevTools] Route synthetic gestures to OOPIF's widget hosts

This follows mouse and touch events in input handler.

Bug: 746266
Change-Id: I10e08dbc6af952e240e6426a145bf1257ccd93ae
Reviewed-on: https://chromium-review.googlesource.com/947470
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541019}
2 files changed