Reviewed by Adam.

        Fixed <rdar://problem/4844848> REGRESSION: extra cross-library ref/deref 
        calls cause .5% PLT regression.
        
        Changed ref/deref calls to a single 'xxxDestroyed' call. Moved EditorClient
        from the Frame to the Page, since it's only responsible for
        Webview-level delegate calls.
        
        I don't really love this design, but it fixes the regression and allows
        a single WebKit object to implement multiple client interfaces.
        
        Layout tests pass.

WebKit:

        Reviewed by Adam.

        Fixed <rdar://problem/4844848> REGRESSION: extra cross-library ref/deref 
        calls cause .5% PLT regression.
        
        Changed ref/deref calls to a single 'xxxDestroyed' call. Moved EditorClient
        from the Frame to the Page, since it's only responsible for
        Webview-level delegate calls.
        
        I don't really love this design, but it fixes the regression and allows
        a single WebKit object to implement multiple client interfaces.
        
        Layout tests pass.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@17906 268f45cc-cd09-0410-ab3c-d52691b4dbfc