tree 4ae09adfde05f24e8dabd397daae9f99d14a1a2f
parent 170b95cf9565b12eb42d419400740b81ce6d7721
author bokan <bokan@chromium.org> 1427328637 -0700
committer Commit bot <commit-bot@chromium.org> 1427328684 +0000

Move viewport scrolling logic into separate class

The viewport is made up of two scrolling layers now, the inner
and outer viewport scroll layers. These layers do not follow the
usual scroll bubbling logic since they're supposed to appear as
one viewport to the user (i.e. we should rail). Forcing it to
be scrolled via LayerTreeHostImpl::ScrollBy caused that method to
become increasingly complex.

This patch creates a Viewport class that allows LTHI::ScrollBy to
call Viewport::ScrollBy and scroll the viewport as a unit. I've
tried to simplify the logic in both these methods as much as I
could without changing behavior.

BUG=443724

Review URL: https://codereview.chromium.org/986443003

Cr-Commit-Position: refs/heads/master@{#322268}