Remove usage of FrameLoaderType in HistoryController

Subsitute it with a special enum specific to history state.

Also, remove some FrameLoader manipulation in HistoryController that doesn't
appear to be necessary.

BUG=none

Review URL: https://codereview.chromium.org/103773003

git-svn-id: svn://svn.chromium.org/blink/trunk@164195 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove the concept of a non-deferred SubstituteData load.

It's only used when creating a worker context, and even then it doesn't appear
to actually be necessary.

BUG=

Review URL: https://codereview.chromium.org/118343006

git-svn-id: svn://svn.chromium.org/blink/trunk@164196 bbb929c8-8fbe-4397-9dbb-9b2b20218538