Replace string16 with base::string16 in gpu, media, and remoting.

R=piman@chromium.org, scherkus@chromium.org, sergeyu@chromium.org
TBR=piman, scherkus, wez

Review URL: https://codereview.chromium.org/114613002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240484 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240484
Replace string16 with base::string16 in chrome/browser

TBR=sky

Review URL: https://codereview.chromium.org/108123004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240485 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240485