Update serial API.

Original CL: https://codereview.chromium.org/27246008

TBR=miket@chromium.org
BUG=155861,148741,140125,169555,171948,281908

Review URL: https://codereview.chromium.org/81053003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236538 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236538