Bug 546169 - Use an event listener instead of a timeout to avoid intermittent failures. r=gavin
Bug 928806 - Allow SharedPlanarYCbCrImage images to optionally have padding. r=nical

Overload YCbCrImageDataSerializer.InitializeBufferInfo to take explicit plane
offsets. Make SharedPlanarYCbCrImage::SetDataNoCopy set the offsets based on the
Y, Cb and Cr plane pointers passed by the caller.