Stop sending notifications of programmatic scrolls.

This code was part of the feature that allowed developers to
 hide the top controls (e.g. the url bar) by calling 
scrollTo. This feature was never launched and never will be. 
See bug for further details.

This effectively reverts the following patches:
https://codereview.chromium.org/18358004/
https://codereview.chromium.org/14114007/

The Chromium patch for deleting this feature is here:
https://codereview.chromium.org/26887008/

BUG=295887

Review URL: https://codereview.chromium.org/26816002

git-svn-id: svn://svn.chromium.org/blink/trunk@160334 bbb929c8-8fbe-4397-9dbb-9b2b20218538