Disable legacy touch event APIs on desktop

In this cl, we make touch-events feature in chrome://flag
default to be disabled.

TouchEvent APIs:
- ontouch* members on window, document, Element
- document.createTouch, document.createTouchList
- document.createEvent("TouchEvent")
will be disabled by default on desktop.

Intent to Deprecate and Remove:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/KV6kqDJpYiE

Bug: 392584
Change-Id: I76716f3c4e529e5143bace95ae1b637b461c2ff5
Reviewed-on: https://chromium-review.googlesource.com/729220
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Navid Zolghadr <nzolghadr@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Commit-Queue: Ella Ge <eirage@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526001}
4 files changed