Bug 1101823 part 1.  Refactor testCommonGetterSetter to just return a boolean indicating whether it's OK to proceed with the common getter/setter, and put the shape guards, into outparams.  r=efaust
Bug 1101823 part 2.  Make sure to add the guard on the global shape to the operands of our DOM getter, if we have such a guard at all.  r=efaust