Revert 46567 - Reimplement accessibility of web content by caching the entire...

Revert 46567 - Reimplement accessibility of web content by caching the entire 
accessibility tree in the browser process.

Adds new RPCs for a browser tab to request accessibility info from
a renderer; the renderer responds with a complete tree of
accessibility metadata for the entire DOM, which is then cached
in the RenderWidgetHostView. This part is crossplatform and will
help with accessibility on both Windows and Mac OS X.

For Windows, MSAA support for web content has been rewritten to
use this new cache. Tested in JAWS and NVDA screen readers.
Using Chrome with a screen reader is now fast and stable,
unlike the previous implementation. However, note that most
advanced functionality is still not supported, and much work remains
to make Chrome work well with a screen reader. This is a necessary
step to improve stability first.

BUG=25564
BUG=13291
TEST=See http://codereview.chromium.org/1806001

Review URL: http://codereview.chromium.org/1637018

TBR=dmazzoni@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=46642

[dmazzoni, 2010-05-07 01:25:33]

LGTM

Sorry this CL caused problems! What test was failing?