Move the remainder of Archive loading from FrameLoader to DocumentLoader.

Currently, when loading a subframe, FrameLoader checks very early on whether
this is a subframe of an archive and switches to an archive load. There's no
obvious reason this is necessary, and checking for a subframe archive load much
later allows us to make everything archive-related on DocumentLoader private.

BUG=none
TEST=none

Review URL: https://chromiumcodereview.appspot.com/14995003

git-svn-id: svn://svn.chromium.org/blink/trunk@149768 bbb929c8-8fbe-4397-9dbb-9b2b20218538
4 files changed