shill: teach dbus_adaptor (and appropriate subclasses) how
to clear properties

BUG=chromium-os:24814
TEST=new unit tests

Change-Id: Ifad5ad0ad6c00d906bade7e1293540a58ac15625
Reviewed-on: https://gerrit.chromium.org/gerrit/15291
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Tested-by: mukesh agrawal <quiche@chromium.org>
Commit-Ready: mukesh agrawal <quiche@chromium.org>
diff --git a/mock_property_store.h b/mock_property_store.h
index 26f5770..d7f23f8 100644
--- a/mock_property_store.h
+++ b/mock_property_store.h
@@ -35,6 +35,7 @@
   MOCK_METHOD3(SetUint8Property, bool(const std::string&, uint8, Error*));
   MOCK_METHOD3(SetUint16Property, bool(const std::string&, uint16, Error*));
   MOCK_METHOD3(SetUint32Property, bool(const std::string&, uint32, Error*));
+  MOCK_METHOD2(ClearProperty, bool(const std::string&, Error*));
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MockPropertyStore);