Move Navigation Timing and other various window-level objects out of page/

Navigation Timing actually has its own spec, so I moved it to its own "timing" directory.

I moved a bunch of the rest of the idls in page into a new frame/ directory.

I'll move Frame.h and friends in their own CL as they're included by 500+ files.

BUG=305811
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/26848007

git-svn-id: svn://svn.chromium.org/blink/trunk@159402 bbb929c8-8fbe-4397-9dbb-9b2b20218538