REGRESSION (r182215): Reproducible crash at drawsvg.org due to reentrant layout

REGRESSION (r182215): Reproducible crash at drawsvg.org due to reentrant layout
https://bugs.webkit.org/show_bug.cgi?id=145964

Reviewed by Simon Fraser.

Source/WebCore:

Test: svg/as-object/mutate-on-load.html

* page/FrameView.cpp:
(WebCore::FrameView::forceLayoutParentViewIfNeeded): Don't do a synchronous layout here,
because it can lead indirectly to unwanted layout reentrancy. Instead schedule a layout.

LayoutTests:

* svg/as-object/mutate-on-load-expected.html: Added.
* svg/as-object/mutate-on-load.html: Added.
* svg/as-object/resources/embedded-mutates-on-load.svg: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@185567 268f45cc-cd09-0410-ab3c-d52691b4dbfc