Reviewed by Adele Peterson.

        REGRESSION: Autoscroll does not work in Mail messages
        https://bugs.webkit.org/show_bug.cgi?id=38267
        rdar://problem/7559799

        The machinery to make autoscrolling work on Mac OS X when a WebView is embedded in another
        view had gotten broken in multiple ways. For some reason, a combination of bugs made it
        partly work until around r48064. This brings it back.

        * WebCoreSupport/WebChromeClient.mm:
        (WebChromeClient::scrollRectIntoView): When converting coordinates, use the document view
        rather than the WebView itself. This logic may not be correct for the case where
        usesDocumentViews is NO, but that is currently an experimental mode and can be fixed later.
2010-04-28  Darin Adler  <darin@apple.com>

        Reviewed by Adele Peterson.

        REGRESSION: Autoscroll does not work in Mail messages
        https://bugs.webkit.org/show_bug.cgi?id=38267
        rdar://problem/7559799

        Still haven't figured out a good way to test this with DumpRenderTree
        or with Safari. Testing has to be done with Mail for now.

        The machinery to make autoscrolling work on Mac OS X when a WebView is embedded in another
        view had gotten broken in multiple ways. For some reason, a combination of bugs made it
        partly work until around r48064. This brings it back.

        There were three problems:

            1) Code in EventHandler decided there was nothing to scroll, so didn't start
               the autoscroll timer.
            2) The wrong rectangle was passed to Chrome::scrollRectIntoView.
            3) The Mac WebKit implementation of ChromeClient::scrollRectIntoView did incorrect
               coordinate conversion.

        I verified that none of these have any effect on regression tests, or behavior in
        web browsers, or behavior on platforms other than Mac.

        * page/EventHandler.cpp:
        (WebCore::canAutoscroll): Added. Returns true for boxes that can scroll directly
        and for the top level box of the top frame.
        (WebCore::EventHandler::handleMouseDraggedEvent): Use canAutoscroll.
        (WebCore::EventHandler::updateAutoscrollRenderer): Ditto.

        * page/FrameView.cpp:
        (WebCore::FrameView::scrollToAnchor): Fixed comment.

        * platform/ScrollView.cpp:
        (WebCore::ScrollView::scrollRectIntoViewRecursively): Put ASSERT_NOT_REACHED into this
        now-unused function along with some comments about removing some obsolete code.

        * rendering/RenderLayer.cpp:
        (WebCore::RenderLayer::scrollRectToVisible): Removed call to scrollRectIntoViewRecursively
        since from the WebKit point of view this is the topmost scroll view anyway. Instead call
        setScrollPosition. Moved the code to call Chrome::scrollRectIntoView here since it needs
        to use a different rectangle anyway.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@58428 268f45cc-cd09-0410-ab3c-d52691b4dbfc