nvda

8c2eb2ea - Make sure that the base virtualBuffer knows nothing about IAccessible and window handles:

Make sure that the base virtualBuffer knows nothing about IAccessible and window handles: *Add a getIdentifierFromNVDAObject method to the base virtualBuffer which is not implemented. Use it where ever we have previously manually retreaved this info. *Implement getIdentifierFromNVDAObject in the Gecko virtualBuffer. *Remove the windowHandle property from the base virtualBuffer (not used). *Rename the rootWindowHandle property on the base virtualBuffer to rootDocHandle.