Reviewed by Dave.

      - instead of walking the render tree to update widget positions, instead
	keep a set of widgets per canvas, maintained by the constructor and destroy method
	for RenderWidget. About a .5% speedup.

        * khtml/khtmlview.cpp:
        (KHTMLView::layout):
        * khtml/rendering/render_canvas.cpp:
        (RenderCanvas::updateWidgetPositions):
        (RenderCanvas::addWidget):
        (RenderCanvas::removeWidget):
        * khtml/rendering/render_canvas.h:
        * khtml/rendering/render_frames.cpp:
        (RenderPart::updateWidgetPosition):
        (RenderPart::needWidgetPositionUpdating):
        * khtml/rendering/render_frames.h:
        * khtml/rendering/render_layer.cpp:
        (khtml::RenderLayer::scrollToOffset):
        * khtml/rendering/render_object.cpp:
        (RenderObject::updateWidgetPosition):
        (RenderObject::needWidgetPositionUpdating):
        * khtml/rendering/render_object.h:
        * khtml/rendering/render_replaced.cpp:
        (RenderWidget::RenderWidget):
        (RenderWidget::destroy):
        (RenderWidget::updateWidgetPosition):
        (RenderWidget::needWidgetPositionUpdating):
        * khtml/rendering/render_replaced.h:


git-svn-id: svn://svn.chromium.org/blink/trunk@10871 bbb929c8-8fbe-4397-9dbb-9b2b20218538