[tf.data] Internal refactoring of C++ classes and APIs.

- replacing `OpKernelContext` with newly introduced `DatasetContext` in `DatasetBase` constructor to make it possible to instantiate `DatasetBase` in places where an instance of `OpKernelContext` is not available

- replacing `dataset::MakeIteratorContext(OpKernelContext* ctx)` factory with `IteratorContext(OpKernelContext *ctx)` constructor.

- folding `GraphDatasetBase` into `DataseBase` and removing the default implementation of `AsGraphDefInternal`, making it the responsibility of the derived class to implement it to encourage/hint developers to provide serialization logic

PiperOrigin-RevId: 208560010

1 files changed, 4 insertions, 3 deletions

diff --git a/tensorflow/contrib/hadoop/kernels/hadoop_dataset_ops.cc b/tensorflow/contrib/hadoop/kernels/hadoop_dataset_ops.cc
index b510994152..80b2d3e08b 100644
--- a/tensorflow/contrib/hadoop/kernels/hadoop_dataset_ops.cc
+++ b/tensorflow/contrib/hadoop/kernels/hadoop_dataset_ops.cc
@@ -204,11 +204,11 @@ class SequenceFileDatasetOp : public DatasetOpKernel {
   }
 
  private:
-  class Dataset : public GraphDatasetBase {
+  class Dataset : public DatasetBase {
    public:
     Dataset(OpKernelContext* ctx, const std::vector<string>& filenames,
             const DataTypeVector& output_types)
-        : GraphDatasetBase(ctx),
+        : DatasetBase(DatasetContext(ctx)),
           filenames_(filenames),
           output_types_(output_types) {}
 
@@ -233,7 +233,8 @@ class SequenceFileDatasetOp : public DatasetOpKernel {
     }
 
    protected:
-    Status AsGraphDefInternal(DatasetGraphDefBuilder* b,
+    Status AsGraphDefInternal(SerializationContext* ctx,
+                              DatasetGraphDefBuilder* b,
                               Node** output) const override {
       Node* filenames = nullptr;
       TF_RETURN_IF_ERROR(b->AddVector(filenames_, &filenames));