Add a few missing scopes to certain RDD methods

core/src/main/scala/org/apache/spark/rdd/RDD.scala

@@ -317,7 +317,9 @@ abstract class RDD[T: ClassTag](
   /**
    * Return a new RDD containing the distinct elements in this RDD.
    */
-  def distinct(): RDD[T] = distinct(partitions.length)
+  def distinct(): RDD[T] = withScope {
+    distinct(partitions.length)
+  }
 
   /**
    * Return a new RDD that has exactly numPartitions partitions.
@@ -429,7 +431,7 @@ abstract class RDD[T: ClassTag](
   def takeSample(
       withReplacement: Boolean,
       num: Int,
-      seed: Long = Utils.random.nextLong): Array[T] = {
+      seed: Long = Utils.random.nextLong): Array[T] = withScope {
     val numStDev =  10.0
 
     if (num < 0) {
@@ -487,7 +489,9 @@ abstract class RDD[T: ClassTag](
    * Return the union of this RDD and another one. Any identical elements will appear multiple
    * times (use `.distinct()` to eliminate them).
    */
-  def ++(other: RDD[T]): RDD[T] = this.union(other)
+  def ++(other: RDD[T]): RDD[T] = withScope {
+    this.union(other)
+  }
 
   /**
    * Return this RDD sorted by the given key function.
@@ -567,8 +571,9 @@ abstract class RDD[T: ClassTag](
    * aggregation (such as a sum or average) over each key, using [[PairRDDFunctions.aggregateByKey]]
    * or [[PairRDDFunctions.reduceByKey]] will provide much better performance.
    */
-  def groupBy[K](f: T => K)(implicit kt: ClassTag[K]): RDD[(K, Iterable[T])] =
+  def groupBy[K](f: T => K)(implicit kt: ClassTag[K]): RDD[(K, Iterable[T])] = withScope {
     groupBy[K](f, defaultPartitioner(this))
+  }
 
   /**
    * Return an RDD of grouped elements. Each group consists of a key and a sequence of elements
@@ -579,8 +584,11 @@ abstract class RDD[T: ClassTag](
    * aggregation (such as a sum or average) over each key, using [[PairRDDFunctions.aggregateByKey]]
    * or [[PairRDDFunctions.reduceByKey]] will provide much better performance.
    */
-  def groupBy[K](f: T => K, numPartitions: Int)(implicit kt: ClassTag[K]): RDD[(K, Iterable[T])] =
+  def groupBy[K](
+      f: T => K,
+      numPartitions: Int)(implicit kt: ClassTag[K]): RDD[(K, Iterable[T])] = withScope {
     groupBy(f, new HashPartitioner(numPartitions))
+  }
 
   /**
    * Return an RDD of grouped items. Each group consists of a key and a sequence of elements
@@ -739,7 +747,7 @@ abstract class RDD[T: ClassTag](
     mapPartitionsWithIndex { (index, iter) =>
       val a = constructA(index)
       iter.map(t => {f(t, a); t})
-    }.foreach(_ => {})
+    }
   }
 
   /**