Bug 874726 -split ShmemYCbCrImage into YCbCrImageDataSerializer and YCbCrImageDataDeserializer. r=jrmuizel

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rename : gfx/layers/ipc/ShmemYCbCrImage.cpp => gfx/layers/YCbCrImageDataSerializer.cpp
rename : gfx/layers/ipc/ShmemYCbCrImage.h => gfx/layers/YCbCrImageDataSerializer.h