Made Serializer and JavaSerializer non private.

core/src/main/scala/spark/JavaSerializer.scala

@@ -57,6 +57,6 @@ private[spark] class JavaSerializerInstance extends SerializerInstance {
   }
 }
 
-private[spark] class JavaSerializer extends Serializer {
+class JavaSerializer extends Serializer {
   def newInstance(): SerializerInstance = new JavaSerializerInstance
 }

core/src/main/scala/spark/Serializer.scala

@@ -9,10 +9,10 @@ import it.unimi.dsi.fastutil.io.FastByteArrayOutputStream
 import spark.util.ByteBufferInputStream
 
 /**
- * A serializer. Because some serialization libraries are not thread safe, this class is used to 
+ * A serializer. Because some serialization libraries are not thread safe, this class is used to
  * create SerializerInstances that do the actual serialization.
  */
-private[spark] trait Serializer {
+trait Serializer {
   def newInstance(): SerializerInstance
 }
 
@@ -88,7 +88,7 @@ private[spark] trait DeserializationStream {
       }
       gotNext = true
     }
-    
+
     override def hasNext: Boolean = {
       if (!gotNext) {
         getNext()