shill: Add support for Cellular.SupportNetworkScan property.

BUG=chromium-os:25851
TEST=unit tests

Change-Id: Ie402be0144f6f8d408ebfd8d904044e7bd20e890
Reviewed-on: https://gerrit.chromium.org/gerrit/15225
Commit-Ready: Darin Petkov <petkov@chromium.org>
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Darin Petkov <petkov@chromium.org>
diff --git a/cellular_capability.h b/cellular_capability.h
index 18fc523..78d9524 100644
--- a/cellular_capability.h
+++ b/cellular_capability.h
@@ -165,6 +165,7 @@
 
   // Properties
   bool allow_roaming_;
+  bool scanning_supported_;
   std::string carrier_;
   std::string meid_;
   std::string imei_;