Revert "Pinch zoom is enabled by default"

This reverts commit 9d27a36fdd3727d7fdebe96fd24013bc601a58df.

BUG=chromium:631549
TEST=Manually tested and related regression tests are disbaled

Change-Id: Ia8c566eec84703a5d86ac9b4b019d51165b2281d
Reviewed-on: https://chromium-review.googlesource.com/363491
Commit-Ready: Amirhossein Simjour <asimjour@chromium.org>
Tested-by: Amirhossein Simjour <asimjour@chromium.org>
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>