Revert 164120 - content/browser: Move more files into the content namespace.

Revert 164120 - content/browser: Move more files into the content namespace.

Fixed most of the files found with the following command line:

$ git grep --files-without-match --name-only "namespace content {" -- content/browser/{*.cc,*.h.*.mm}

R=jam@chromium.org

Review URL: https://codereview.chromium.org/11274038

TBR=tfarina@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=164122