Revert 232881 "cc: Fix hit-testing in zero-opacity layers."

Reverting because this broke scrolling on mobile GMail.

> cc: Fix hit-testing in zero-opacity layers.
> 
> If a layer that accepts touch or wheel events, but the layer (or one of its
> ancestor layers) has zero opacity, then make sure the layer hit-tests correctly.
> 
> BUG=295295
> R=enne@chromium.org, rbyers@google.com
> 
> Review URL: https://codereview.chromium.org/26112002

TBR=sadrul@chromium.org
BUG=318088,313523

Review URL: https://codereview.chromium.org/68933008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234482 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234482