Sign Native Messaging binaries on mac

The previous fix in r252903 (--deep parameter for codesign) didn't help
presumably because the signing bot uses an older version of the
codesign tool that doesn't support --deep. Updated do_signing.sh script
to sign the binaries explicitly.

BUG=345967
R=jamiewalch@chromium.org

Review URL: https://codereview.chromium.org/181673004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253690 0039d316-1c4b-4281-b951-d872f2087c98
Remove "OVERRIDE" from the deprecated MockPeerConnectionImpl::GetStats
so that the method can be removed from the interface from third_party/libjingle.

Review URL: https://codereview.chromium.org/171663003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253691 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253691