Revert 232393 "Enable universal overflow scrolling by default."

This is causing layer explosions. Let's turn this off by default until we have a
solution for this problem.

> Enable universal overflow scrolling by default.
> 
> BUG=
> 
> Review URL: https://codereview.chromium.org/55083002

TBR=hartmanng@chromium.org

Review URL: https://codereview.chromium.org/58063003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232776 0039d316-1c4b-4281-b951-d872f2087c98
Optimize png files in ui/resources ash/resources

$./tools/resources/optimize-png-files.sh -o2 -r224739 ui/resources/ ash/resources/

Processed 36 files (out of 36 files) in 00:01:50s
Result : 14857 => 6816 bytes (8041 bytes : 54 %)

BUG=313729
TBR=jamescook@chromium.org

Review URL: https://codereview.chromium.org/58363002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232777 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232776
SVN changes up to revision 232777