NaCl SDK: Remove PPB_Testing_Dev.

This interface shouldn't be used by anything in native_client_sdk.

BUG=
R=binji@chromium.org

Review URL: https://codereview.chromium.org/66153004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236045 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236045