Reviewed by Dan Bernstein.

        Bug 23538: REGRESSION (r39969): Garbage text instead of blank content rendered when plug-ins are disabled
        https://bugs.webkit.org/show_bug.cgi?id=23538
        rdar://problem/6523719

        I'm not sure how to make a regression test for this, since it depends on plug-ins being disabled.

        The main problem here is that when plug-ins were disabled, the code ignored the classId attribute and
        the <embed> element entirely. That resulted in a page treating a Flash document as plain HTML rather
        than doing fallback.

        * rendering/RenderPartObject.cpp:
        (WebCore::createClassIdToTypeMap): Added. Broke this out into a separate function so we could get rid of an
        inelegant if statement.
        (WebCore::activeXType): Added. To avoid repeating the MIME type for ActiveX and possibly having a typo.
        (WebCore::havePlugin): Added. Helper function to make sure we don't forget the null check.
        (WebCore::serviceTypeForClassId): Give this function a return value since that's a more natural way to
        return a string than an "out" parameter.  Fixed the logic to only prefer the ActiveX type over the
        type guessed from the classId when there actually is an ActiveX plug-in to use. The old function assumed
        there was one, which I presume right for Chrome on Windows when plug-ins are enabled, but wrong in many
        other cases, and wrong all the time for all clients on Mac. We don't want to assume either way. Use the
        new havePlugin function so we handle the case where pluginData is 0.
        (WebCore::shouldUseEmbedDescendant): Renamed. Simplified the comment. Changed to use serviceTypeForClassId
        instead of the old version that used an out parameter. Always use the <embed> if there isn't a plug-in
        that knows how to handle <object> elements.
        (WebCore::RenderPartObject::updateWidget): Removed null checks of pluginData. The two functions that
        use this data still need to be called; they still do something even if no plug-ins are present. And
        they have now been corrected to handle 0 properly.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@40234 268f45cc-cd09-0410-ab3c-d52691b4dbfc