Revert of Make same-document history navigations commit with the proper type. (https://codereview.chromium.org/252323003/)

Reason for revert:

Sorry to revert this change. It seems to have broken the following test in content_browsertests:
WebContentsViewAuraTest.OverscrollScreenshot

Log: http://build.chromium.org/p/chromium.webkit/builders/Linux%20Tests/builds/36417/steps/content_browsertests/logs/OverscrollScreenshot

Snippet from log: 
terminate called after throwing an instance of 'std::out_of_range'
  what():  vector::_M_range_check

Original issue's description:
> Make same-document history navigations commit with the proper type.
> 
> There is a quirk in HistoryController where we commit a history navigation immediately upon starting a same-document navigation. If a same-document history navigation is committed with a HistoryCommitType of BackForwardCommit instead of HistoryInertCommit, the commit logic does the right thing and we don't need that quirk.
> 
> BUG=
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=173142

TBR=abarth@chromium.org,japhet@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/265003002

git-svn-id: svn://svn.chromium.org/blink/trunk@173176 bbb929c8-8fbe-4397-9dbb-9b2b20218538