Revert 227318 "Clean up ResourceHandler API."

Could be causing http://crbug.com/305333.

> Clean up ResourceHandler API.
> 
> 1. Move URLRequest member to ResourceHandler base class and add convenience functions for subclasses.
> 2. Make OnWillRead take a scoped_refptr to avoid leaking the buffer.
> 
> BUG=295239
> TEST=No behavior change.
> 
> Review URL: https://codereview.chromium.org/25536005

TBR=creis@chromium.org

Review URL: https://codereview.chromium.org/26472004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227594 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227594