[CastRunner] Allow Agent's enable-touch bindings to supercede the Runner's.

Prevents the CastRunner from clobbering the Agent's
setTouchSupportEnabled() platform API if it's already been installed.

Bug: 953796,953958
Change-Id: Ia1044a96209f04d792a8c671a8ac18eb98b2d9ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1728445
Reviewed-by: Fabrice de Gans-Riberi <fdegans@chromium.org>
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683227}
1 file changed