Use base namespace for string16 in chrome/browser.

This converts 200 more files.

TBR=sky

Review URL: https://codereview.chromium.org/108353004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239278 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239278
Add myself to OWNERS for IPC messages.

BUG=none
R=jam@chromium.org, palmer@chromium.org

Review URL: https://codereview.chromium.org/100823011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239279 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239279