Revert of Pinch/Zoom Infrastructure & Plumbing CL (https://codereview.chromium.org/23983047/)

Reason for revert:
This patch broke several blink-side compositing/rtl tests[1][2]. It's
unclear whether these tests are valuable, given some comments
in TestExpectations, but since I know nothing about compositing
I'll leave the decision about what to do with these tests up to
someone who does.

[1]: http://test-results.appspot.com/dashboards/flakiness_dashboard.html#group=%40ToT%20Blink&tests=compositing/rtl/rtl-iframe-absolute-overflow-scrolled.html,compositing/rtl/rtl-iframe-absolute-overflow.html,compositing/rtl/rtl-iframe-fixed-overflow-scrolled.html,compositing/rtl/rtl-iframe-fixed-overflow.html
[2]: http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Mac10.7/builds/22131

Original issue's description:
> Pinch/Zoom Infrastructure & Plumbing CL
> 
> This CL supplies the necessary changes to CC to support the
> inner/outer viewport model for pinch-zoom and fixed-position 
> elements. The specification for these changes is contained in 
> the document "Layer-based Solution for Pinch Zoom / Fixed 
> Position".
> 
> It incorporates a change to how scrollbar parameters are 
> computed (removes the notion of max_scroll_offset as a 
> quantity set be the embedder, and instead inferred from the 
> relative sizes of a clip layer w.r.t. the scroll layer).
> 
> Scrollbars are generalized so that a layer may have more than 
> two scrollbars, and the parameters of the scrollbar are set 
> w.r.t. the sizes and positions of a clip and a scroll layer. 
> Further, changes to the scrip/scroll layer automatically 
> notify any attached scrollbars.
> 
> The CL also removes existing references to root_scroll_layer 
> from LTH, LTI and LTHI and replaces them with either 
> Inner/OuterViewportScrollLayer (dual-layer operation only 
> exists at present if the --enable-pinch-virtual-viewport flag 
> is specified, otherwise behavior is unchanged).
> 
> Logic is added to (i) combine scroll offsets for the two 
> viewports before passing it to the embedder, and (ii) 
> splitting any offsets received from the embedder 
> appropriately between the two viewports.
> 
> This CL relies on https://codereview.chromium.org/138453004/ 
> for changes in Blink to support it.
> 
> BUG=148816
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=246812

TBR=enne@chromium.org,aelias@chromium.org,joi@chromium.org,sky@chromium.org,piman@chromium.org,tony@chromium.org,wjmaclean@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=148816

Review URL: https://codereview.chromium.org/146713002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246842 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246842