REGRESSION (r143619): Crashes in three layout tests
https://bugs.webkit.org/show_bug.cgi?id=110588

Patch by Martin Robinson <mrobinson@igalia.com> on 2013-02-26
Reviewed by Gustavo Noronha Silva.

Source/WebKit/gtk:

Guard against null main resource identifiers. The main resource
identifier can be null at various times during the load. A null
identifier is never equal to the ones we are looking to remove.

* WebCoreSupport/FrameLoaderClientGtk.cpp:
(WebKit::FrameLoaderClient::dispatchDidFinishLoading): Use the new webkitWebViewRemoveSubresource helper.
(WebKit::FrameLoaderClient::dispatchDidFailLoading): ditto.
* webkit/webkitwebview.cpp:
(webkitWebViewRemoveSubresource): Added this helper which removes a subresource, but
never touches the main resource. This is adapted from the old method, for which the
main resource branch was dead code.
* webkit/webkitwebviewprivate.h: Update the method list.

LayoutTests:

* platform/gtk/TestExpectations: Unskip some tests which are no longer
crashing.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144055 268f45cc-cd09-0410-ab3c-d52691b4dbfc