Fix test failures and mark a couple variables private

Author: sryza

core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleWriter.scala

@@ -39,7 +39,7 @@ private[spark] class HashShuffleWriter[K, V](
   // we don't try deleting files, etc twice.
   private var stopping = false
 
-  val writeMetrics = new ShuffleWriteMetrics()
+  private val writeMetrics = new ShuffleWriteMetrics()
   metrics.shuffleWriteMetrics = Some(writeMetrics)
 
   private val blockManager = SparkEnv.get.blockManager

core/src/main/scala/org/apache/spark/shuffle/sort/SortShuffleWriter.scala

@@ -52,7 +52,7 @@ private[spark] class SortShuffleWriter[K, V, C](
 
   private var mapStatus: MapStatus = null
 
-  val writeMetrics = new ShuffleWriteMetrics()
+  private val writeMetrics = new ShuffleWriteMetrics()
   context.taskMetrics.shuffleWriteMetrics = Some(writeMetrics)
 
   /** Write a bunch of records to this task's output */

core/src/main/scala/org/apache/spark/storage/BlockObjectWriter.scala

@@ -186,7 +186,7 @@ private[spark] class DiskBlockObjectWriter(
   }
 
   override def fileSegment(): FileSegment = {
-    new FileSegment(file, initialPosition, writeMetrics.shuffleBytesWritten)
+    new FileSegment(file, initialPosition, finalPosition - initialPosition)
   }
 
   private def updateBytesWritten() {