message: Make the XLA CpuTransferManager reflect the fact that the allocator is
  synchronous and buffers can be accessed immediately.
diff: @@ -44,6 +44,12 @@ class CpuTransferManager : public GenericTransferManager {
  const Shape& literal_shape,
  MutableBorrowingLiteral literal) override;
  + bool CanShapedBufferBeAccessedNow(
  + se::StreamExecutor* executor,
  + const ShapedBuffer& device_buffer) const override {
  + return true;
  + }
  +
  private:
  Status TransferBufferToInfeed(se::StreamExecutor* executor, int64 size,
  const void* source);
  