[Chromium] Refactor WebFrameImpl::createFrameView() to use Frame:createView

[Chromium] Refactor WebFrameImpl::createFrameView() to use Frame:createView
https://bugs.webkit.org/show_bug.cgi?id=70507

Reviewed by Darin Fisher.

No change in functionality except for fixed layout mode. Fixed layout mode has
not been fully upstreamed yet, so no new tests yet:
https://bugs.webkit.org/show_bug.cgi?id=70562 will address this.

This patch also fixes https://bugs.webkit.org/show_bug.cgi?id=70555
It was decided that fixed layout mode might need to be disabled for some content,
and so this change enables the embedder to decide whether to enable fixed layout on
navigation.

* src/WebFrameImpl.cpp:
(WebKit::WebFrameImpl::createFrameView):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@99208 268f45cc-cd09-0410-ab3c-d52691b4dbfc