shill: Broadcast serving cellular operator property changes.

BUG=chromium-os:25011
TEST=unit tests

Change-Id: I52867ef2a95b8babd418ff64d33435c0b54b6ab8
Reviewed-on: https://gerrit.chromium.org/gerrit/14987
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Eric Shienbrood <ers@chromium.org>
Commit-Ready: Darin Petkov <petkov@chromium.org>
diff --git a/cellular_capability_gsm.cc b/cellular_capability_gsm.cc
index 1590ac9..c79501b 100644
--- a/cellular_capability_gsm.cc
+++ b/cellular_capability_gsm.cc
@@ -296,7 +296,7 @@
 void CellularCapabilityGSM::UpdateServingOperator() {
   VLOG(2) << __func__;
   if (cellular()->service().get()) {
-    cellular()->service()->set_serving_operator(serving_operator_);
+    cellular()->service()->SetServingOperator(serving_operator_);
   }
 }