Mojo: Add ErrorHandler to RemotePtr

BUG=325321
R=davemoore@chromium.org

Review URL: https://codereview.chromium.org/150713002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248094 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248094