Reuse tasksupport in CombinerFactory

Fixes #152

Author: lrytz

core/src/main/scala/scala/collection/parallel/ParIterableLike.scala

@@ -550,7 +550,11 @@ extends IterableOnce[T @uncheckedVariance]
       def apply() = shared
       def doesShareCombiners = true
     } else new CombinerFactory[T, Repr] {
-      def apply() = newCombiner
+      def apply() = {
+        val r = newCombiner
+        r.combinerTaskSupport = tasksupport
+        r
+      }
       def doesShareCombiners = false
     }
   }
@@ -563,7 +567,11 @@ extends IterableOnce[T @uncheckedVariance]
       def apply() = shared
       def doesShareCombiners = true
     } else new CombinerFactory[S, That] {
-      def apply() = cbf()
+      def apply() = {
+        val r = cbf()
+        r.combinerTaskSupport = tasksupport
+        r
+      }
       def doesShareCombiners = false
     }
   }

junit/src/test/scala/scala/collection/parallel/TaskTest.scala

@@ -39,4 +39,13 @@ class TaskTest {
 
     for (x <- one ; y <- two) assertEquals("two", Thread.currentThread.getName)
   }
+
+  @Test
+  def `t152 pass on task support`(): Unit = {
+    val myTs = new ExecutionContextTaskSupport()
+    val c = List(1).par
+    c.tasksupport = myTs
+    val r = c.filter(_ != 0).map(_ + 1)
+    assertSame(myTs, r.tasksupport)
+  }
 }