Fix by Trey Matteson, reviewed by Maciej.

    Fix by Trey Matteson, reviewed by Maciej.

        http://bugzilla.opendarwin.org/show_bug.cgi?id=7739
        REGRESSION: Assertion failure loading acid2 test in -[WebCoreFrameBridge installInFrame:]

        Tests: http/tests/misc/acid2.html, http/tests/misc/acid2-pixel.html

        The gist of this change is that we must cancel the load from the Webkit side when we
        realize we're switching to the fallback content.  This is somewhat a temp workaround
        since control of loading will be moving to WebCore.

        * WebView/WebMainResourceLoader.m:
        (-[WebMainResourceLoader continueAfterContentPolicy:response:]):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@13615 268f45cc-cd09-0410-ab3c-d52691b4dbfc