Reviewed by Eric Seidel.

        Fixes two bugs about Pan Scrolling - Scrolling with middle mouse button doesn't
        work in Expanded view on reader.google.com, and Can enter auto scroll from a non-scrollable area.
        https://bugs.webkit.org/show_bug.cgi?id=28023
        https://bugs.webkit.org/show_bug.cgi?id=24794

        Added a new method to RenderBox seeing if the Box can be scrolled and actually has something to
        scroll, and use that for pan scrolling.

        Test: platform/win/fast/events/panScroll-nested-divs.html

        * page/EventHandler.cpp:
        (WebCore::EventHandler::handleMouseDraggedEvent):
        (WebCore::EventHandler::updateAutoscrollRenderer):
        (WebCore::EventHandler::handleMousePressEvent):
        * rendering/RenderBox.cpp:
        (WebCore::RenderBox::canBeScrolledAndHasScrollableArea):
        * rendering/RenderBox.h:
        * rendering/RenderLayer.cpp:
        (WebCore::RenderLayer::scrollByRecursively):

2009-08-12  Brian Weinstein  <bweinstein@apple.com>

        Reviewed by Eric Seidel.

        Added a Windows test for https://bugs.webkit.org/show_bug.cgi?id=28023.

        * platform/win/fast/events/panScroll-nested-divs-expected.txt: Added.
        * platform/win/fast/events/panScroll-nested-divs.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@47163 268f45cc-cd09-0410-ab3c-d52691b4dbfc