[Sync] Fix namespace for sync_driver component

browser_sync namespace was still in use while transitions were being made.
We're far enough along now that it's worth moving to the sync_driver namespace.

BUG=339728
TBR=bauerb@chromium.org

Review URL: https://codereview.chromium.org/408003002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284799 0039d316-1c4b-4281-b951-d872f2087c98
139 files changed