Replace mountType by volumeType on fileBrowserPrivate APIs.

chromeos/disks/disk_mount_manager.h

Index: chromeos/disks/disk_mount_manager.h
diff --git a/chromeos/disks/disk_mount_manager.h b/chromeos/disks/disk_mount_manager.h
index 36389a0ca98374e36913a772392084c557ab5079..4edc475256855453962a80c55fd70e6db823c5f5 100644
--- a/chromeos/disks/disk_mount_manager.h
+++ b/chromeos/disks/disk_mount_manager.h
@@ -272,12 +272,6 @@ class CHROMEOS_EXPORT DiskMountManager {
   virtual bool AddDiskForTest(Disk* disk);
   virtual bool AddMountPointForTest(const MountPointInfo& mount_point);
 
-  // Returns corresponding string to |type| like "device" or "file".
-  static std::string MountTypeToString(MountType type);
-
-  // The inverse function of MountTypeToString.
-  static MountType MountTypeFromString(const std::string& type_str);
-
   // Returns corresponding string to |type| like "unknown_filesystem".
   static std::string MountConditionToString(MountCondition type);