Move FrameData API into its own header/source files.

This is a follow up  to r155109.

R=eae@chromium.org,jbroman@chromium.org

Review URL: https://chromiumcodereview.appspot.com/21109006

git-svn-id: svn://svn.chromium.org/blink/trunk@155257 bbb929c8-8fbe-4397-9dbb-9b2b20218538