Remove redundant/misleaing README.chromium files.

These files are a legacy from when the native_client_sdk
and ppapi were DEPS'd in from an external repos rather
than being part of chromium.

Second attempt at landing this change.
> Initial: https://codereview.chromium.org/54983002
> Revert:  https://codereview.chromium.org/55983003

Review URL: https://codereview.chromium.org/54673014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233658 0039d316-1c4b-4281-b951-d872f2087c98
Mojo: Accept IDL files that lack explicit ordinals.

R=davemoore@chromium.org

Review URL: https://codereview.chromium.org/63763003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233659 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233659