Merged commit includes the following changes:

175895735  by gunan:

    Move IODataType to a new types.proto in preparation for using it
    in ModelFlags

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175893178  by fchollet:

    Fix multiprocessing issue in keras.utils.data_utils.

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175891377  by jart:

    Use redundant download URLs and fix protobuf def

    I uncommented all the GitHub URLs that turned out to have consistent
    SHAs. The ones that didn't, I left them commented. We can't re-mirror
    those URLs because doing so would cause past revisions of the
    repository to become broken. So workspace.bzl is going to have to
    evolve back to not having these comments, over time, as we continue to
    upgrade stuff.

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175889431  by apassos:

    Fixed order for EagerVariableStore.

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175882680  by A. Unique TensorFlower:

    Move IODataType to a new types.proto in preparation for using it
    in ModelFlags

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PiperOrigin-RevId: 175895735