Simplify same document navigation

Combine the state changes for pushState, replaceState, and standard same
document navigations.

Move some HistoryController commit notification calls from FrameLoader to
FrameLoaderClientImpl.

BUG=321280

Review URL: https://codereview.chromium.org/76543004

git-svn-id: svn://svn.chromium.org/blink/trunk@162385 bbb929c8-8fbe-4397-9dbb-9b2b20218538