Drawing text in an SVG font causes load events to be fired.

Drawing text in an SVG font causes load events to be fired.
<https://webkit.org/b/136269>
<rdar://problem/15724915>

Source/WebCore:

Don't flush pending load events in Document::implicitClose() for frameless documents.
This is a targeted fix for an issue where parsing SVG fonts during layout would cause
event dispatch to happen in the main document, leading to arbitrary JS execution.

Note that the testcase only works in DRT/WTR, since once the SVG font is in cached
by WebCore, we won't reparse it again. Caches are cleared between tests, so it will
correctly fail if this should regress.

Longer-term, we should clean this up and get rid of the global dispatch entirely.

Reviewed by Simon Fraser.

Test: fast/text/svg-font-trigger-load-event.html

* dom/Document.cpp:
(WebCore::Document::implicitClose):

LayoutTests:

Reviewed by Simon Fraser.

* fast/text/svg-font-trigger-load-event-expected.txt: Added.
* fast/text/svg-font-trigger-load-event.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@173028 268f45cc-cd09-0410-ab3c-d52691b4dbfc