shill: Cleanup - private callback methods shouldn't be virtual.

Fix a not-quite-correct comment while here.

BUG=None
TEST=compilation, unit tests pass. No functional change intended.

Change-Id: Iacf194c3aed49db25103685f5a373344a5820379
Reviewed-on: https://gerrit.chromium.org/gerrit/20638
Tested-by: Nathan J. Williams <njw@chromium.org>
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Reviewed-by: Jason Glasgow <jglasgow@chromium.org>
Commit-Ready: Jason Glasgow <jglasgow@chromium.org>
diff --git a/cellular_capability_classic.h b/cellular_capability_classic.h
index c19503f..8778a7c 100644
--- a/cellular_capability_classic.h
+++ b/cellular_capability_classic.h
@@ -129,16 +129,16 @@
       void(CellularCapability::*set)(const bool &value, Error *error));
 
   // Method reply and signal callbacks from Modem interface
-  virtual void OnModemStateChangedSignal(
+  void OnModemStateChangedSignal(
       uint32 old_state, uint32 new_state, uint32 reason);
-  virtual void OnGetModemInfoReply(const ResultCallback &callback,
-                                   const ModemHardwareInfo &info,
-                                   const Error &error);
+  void OnGetModemInfoReply(const ResultCallback &callback,
+                           const ModemHardwareInfo &info,
+                           const Error &error);
 
   // Method reply callbacks from Modem.Simple interface
-  virtual void OnGetModemStatusReply(const ResultCallback &callback,
-                                     const DBusPropertiesMap &props,
-                                     const Error &error);
+  void OnGetModemStatusReply(const ResultCallback &callback,
+                             const DBusPropertiesMap &props,
+                             const Error &error);
 
   Cellular *cellular_;
   base::WeakPtrFactory<CellularCapabilityClassic> weak_ptr_factory_;