r17399 and r17511 moved the functionality of WebElementDictionary into WebCore. However, this caused a behavior change in WebElementDictionary: before, an <a> element with no title attribute would return a nil NSString* when asked for WebElementLinkTitleKey. Now it returns an empty NSString (i.e., ""). This is causing problems with proposed bookmark titles.
Created attachment 11631 [details] testcase
This also raises the question of whether methods like HitTestResult::title() should be able to differentiate between <a> and <a title="">
Fixed with r17919.