shill: implement manager.RequestScan (for WiFi only)

BUG=chromium-os:19831
TEST=unittests, WiFiManager/000_SSID_Length_Limit

note that 000_SSID_Length_Limit does not pass yet,
because we don't do IP configuration yet. but it
does get scan results.

Change-Id: I8993b3c646eda705271d1f7ad7d7341c692ae06b
Reviewed-on: http://gerrit.chromium.org/gerrit/7407
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Tested-by: mukesh agrawal <quiche@chromium.org>
diff --git a/manager_dbus_adaptor.h b/manager_dbus_adaptor.h
index df0eeb9..bc72273 100644
--- a/manager_dbus_adaptor.h
+++ b/manager_dbus_adaptor.h
@@ -41,6 +41,8 @@
   void EmitUintChanged(const std::string &name, uint32 value);
   void EmitIntChanged(const std::string &name, int value);
   void EmitStringChanged(const std::string &name, const std::string &value);
+  void EmitRpcIdentifierArrayChanged(
+      const std::string &name, const std::vector<std::string> &value);
   void EmitStateChanged(const std::string &new_state);
 
   // Implementation of Manager_adaptor