Reviewed by Darin.

        <rdar://problem/5289718>
        http://bugs.webkit.org/show_bug.cgi?id=14437
        CrashTracer: [REGRESSION] 76 crashes in Safari at com.apple.WebCore: WebCore::Frame::settings const + 6 (14437)
        
        Add test from Alexey Proskuryakov.
        
        * plugins/plugin-remove-subframe-expected.txt: Added.
        * plugins/plugin-remove-subframe.html: Added.

WebCore:

        Reviewed by Darin.

        <rdar://problem/5289718>
        http://bugs.webkit.org/show_bug.cgi?id=14437
        CrashTracer: [REGRESSION] 76 crashes in Safari at com.apple.WebCore: WebCore::Frame::settings const + 6 (14437)
        
        Based on a patch from Maxime Britto.
        
        * page/mac/WebCoreFrameBridge.mm:
        (-[WebCoreFrameBridge stringByEvaluatingJavaScriptFromString:forceUserGesture:]):
        If the script caused the frame to go away, return nil. This can only happen if a plugin in a subframe destroys
        its frame.

        (-[WebCoreFrameBridge aeDescByEvaluatingJavaScriptFromString:]):
        ASSERT that this is only called on the main frame.

WebKit:

        Reviewed by Darin.

        * WebView/WebView.mm:
        (-[WebView stringByEvaluatingJavaScriptFromString:]):
        ASSERT that the value returned isn't nil. It can't be nil when invoked on the main frame.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@23950 268f45cc-cd09-0410-ab3c-d52691b4dbfc