Reviewed by Ken.

    Reviewed by Ken.

        - fixed <rdar://problem/3848257> WebView will draw more than AppKit asks it to, so views behind won't redraw enough (transparent WebView)

        * WebView.subproj/WebHTMLView.m:
        (-[WebHTMLView _propagateDirtyRectsToOpaqueAncestors]): As recommended by Troy Stephens, do the
        layouts here in this call, since it's before propagating the dirty rects to our ancestors.
        This fixes the bug, but we only do it if the WebView is not opaque, because otherwise we can
        optimize by only doing layouts you really need, and doing them later on is safe because we
        know we don't need to draw any of the views behind us.
        (-[WebHTMLView _layoutIfNeeded]): Added. Factored out from the method below.
        (-[WebHTMLView _web_layoutIfNeededRecursive]): Added. Like the other "layout if needed" call,
        but unconditional.
        (-[WebHTMLView _web_layoutIfNeededRecursive:testDirtyRect:]): Factored out the guts into the
        _layoutIfNeeded method above. Otherwise unchanged.
        (-[NSView _web_layoutIfNeededRecursive]): Added.

        * WebView.subproj/WebFrame.m: (-[WebFrame _updateDrawsBackground]): Call setDrawsBackground:NO
        on the scroll view when changing the frame to no longer be in "draws background" mode. This
        is needed because the frame manages the "draws background" mode of the scroll view. It won't
        have any effect if you call setDrawsBackground:NO before starting to use a WebView, but without
        it calling setDrawsBackground:NO later won't have an immediate effect (easily visible in Safari).
        This was hidden before because the HTML view was filling with transparent color, which blew away
        the fill that was done by NSScrollView.

        - fixed <rdar://problem/3921129> reproducible crash at www.funnychristmas.com in CFSet manipulation in WebImageData

        * WebCoreSupport.subproj/WebImageData.m:
        (-[WebImageData _imageSourceOptions]): Changed types so we don't need a cast.
        (+[WebImageData stopAnimationsInView:]): Instead of building a set of sets, by putting in the sets with addObject,
        build a single set using unionSet, and then iterate the objects instead of having to iterate the sets and then the
        objects in each set. The old code ended up sharing the sets with the live code, when the whole idea was to gather
        all the renderers because the process of stopping modifies the active sets.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8348 268f45cc-cd09-0410-ab3c-d52691b4dbfc