WebProcess sometimes hits an assertion in SandboxExtensionTracker::didCommitP...

    WebProcess sometimes hits an assertion in SandboxExtensionTracker::didCommitProvisionalLoad after running regression tests
        https://bugs.webkit.org/show_bug.cgi?id=81150
        <rdar://problem/11002254>

        Reviewed by Anders Carlsson.

        * WebProcess/WebPage/WebPage.cpp:
        (WebKit::WebPage::SandboxExtensionTracker::didCommitProvisionalLoad):
        (WebKit::WebPage::SandboxExtensionTracker::didFailProvisionalLoad):
        It's not great, but for now we need to handle this case. Hopefully, some day we'll make
        both WebKit2 processes better aware of what's going on with loading in WebCore.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@110743 268f45cc-cd09-0410-ab3c-d52691b4dbfc