Respect user_scrollable disabling in pinch-virtual-viewport mode.
user_scrollable_x/y are used to suppress impl-side scrolling when the
page specifies overflow: hidden. This has been disabled for a while
because of poor interaction with pinch zoom. In the new pinch-virtual
model, this works better (outer viewport doesn't scroll so that the user
can't see parts of the page not intended to be seen, but pinch zooming
and moving around still works), so re-enable it when that setting is
active.
Note that I'm also planning to start using this for disabling scrolling
for fullscreen elements.
BUG=322223,175502,411072
Review URL: https://codereview.chromium.org/626403003
Cr-Commit-Position: refs/heads/master@{#299428}
5 files changed
