libaddressinput: convert json::Build to scoped_ptr

BUG=none

Review URL: https://codereview.chromium.org/104923013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242242 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242242
Moving the RMQStore Creation and Loading outside of the MCSClient

BUG=284553

Review URL: https://codereview.chromium.org/106523005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242243 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242243