How to user unloadStyleDeclarations?
FlexGlobals.topLevelApplication.styleManager.loadStyleDeclarations(skinName, true);

FlexGlobals.topLevelApplication.styleManager.unloadStyleDeclarations("style/normal.swf",false);

ReferenceError: Error #1069: La property 0 cannot be found on Number
  and there is no default value.
    at normal/unloadOverrides()[null/normal-generated.as:721]
    at normal/unload()[null/normal-generated.as:676]

clearStyleDeclaration()

loadStyleDeclarations()

setStyleDeclaration()

unloadStyleDeclarations()