Reviewed by Oliver.

        * editing/pasteboard/5245519-expected.checksum: Added.
        * editing/pasteboard/5245519-expected.png: Added.
        * editing/pasteboard/5245519-expected.txt: Added.
        * editing/pasteboard/5245519.html: Added.

WebCore:

        Reviewed by Oliver.
        
        <rdar://problem/5245519> CrashTracer: [USER] 457 crashes in Mail at WebCore::CSSComputedStyleDeclaration::copyInheritableProperties()
        
        If the user pastes something into a region that ends up being
        invisible, or if the pasted content contains style spans 
        that are render-less, we'll crash when we try to remove
        redundant styles from style spans.

        * css/CSSComputedStyleDeclaration.cpp:
        (WebCore::CSSComputedStyleDeclaration::copyInheritableProperties):
        Add null checks.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@22038 268f45cc-cd09-0410-ab3c-d52691b4dbfc