Disable link preload when sanitizing web content

https://bugs.webkit.org/show_bug.cgi?id=258100
rdar://109675198

Reviewed by Chris Dumez.

Otherwise we get a request in the network process with an invalid pageID,
and it MESSAGE_CHECKs and terminates the process.

* Source/WebCore/editing/markup.cpp:
(WebCore::createPageForSanitizingWebContent):

Canonical link: https://commits.webkit.org/259548.830@safari-7615-branch

Source/WebCore/editing/markup.cpp

@@ -191,6 +191,7 @@ std::unique_ptr<Page> createPageForSanitizingWebContent()
     page->settings().setHTMLParserScriptingFlagPolicy(HTMLParserScriptingFlagPolicy::Enabled);
     page->settings().setPluginsEnabled(false);
     page->settings().setAcceleratedCompositingEnabled(false);
+    page->settings().setLinkPreloadEnabled(false);
 
     Frame& frame = page->mainFrame();
     frame.setView(FrameView::create(frame, IntSize { 800, 600 }));