Turn UpdateBlockInfo into case class.

This helps us log UpdateBlockInfo properly once #1870 is merged.

Author: Reynold Xin <rxin@apache.org>

Closes #1872 from rxin/UpdateBlockInfo and squashes the following commits:

0cee1c2 [Reynold Xin] Turn UpdateBlockInfo into case class.

(cherry picked from commit 482c5af)
Signed-off-by: Reynold Xin <rxin@apache.org>

Author: rxin

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

@@ -53,7 +53,7 @@ private[spark] object BlockManagerMessages {
       sender: ActorRef)
     extends ToBlockManagerMaster
 
-  class UpdateBlockInfo(
+  case class UpdateBlockInfo(
       var blockManagerId: BlockManagerId,
       var blockId: BlockId,
       var storageLevel: StorageLevel,
@@ -84,24 +84,6 @@ private[spark] object BlockManagerMessages {
     }
   }
 
-  object UpdateBlockInfo {
-    def apply(
-        blockManagerId: BlockManagerId,
-        blockId: BlockId,
-        storageLevel: StorageLevel,
-        memSize: Long,
-        diskSize: Long,
-        tachyonSize: Long): UpdateBlockInfo = {
-      new UpdateBlockInfo(blockManagerId, blockId, storageLevel, memSize, diskSize, tachyonSize)
-    }
-
-    // For pattern-matching
-    def unapply(h: UpdateBlockInfo)
-      : Option[(BlockManagerId, BlockId, StorageLevel, Long, Long, Long)] = {
-      Some((h.blockManagerId, h.blockId, h.storageLevel, h.memSize, h.diskSize, h.tachyonSize))
-    }
-  }
-
   case class GetLocations(blockId: BlockId) extends ToBlockManagerMaster
 
   case class GetLocationsMultipleBlockIds(blockIds: Array[BlockId]) extends ToBlockManagerMaster