dbus: add ObjectPath type

dbus/exported_object.h

Index: dbus/exported_object.h
diff --git a/dbus/exported_object.h b/dbus/exported_object.h
index 7ac2f88445dec5695ee14c9e2eed5f5b3400edcf..560faccf670cdf019b9d9b29cd90dbb5ad9029b6 100644
--- a/dbus/exported_object.h
+++ b/dbus/exported_object.h
@@ -17,6 +17,7 @@
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/platform_thread.h"
 #include "base/time.h"
+#include "dbus/object_path.h"
 
 namespace dbus {
 
@@ -36,7 +37,7 @@ class ExportedObject : public base::RefCountedThreadSafe<ExportedObject> {
   // constructor.
   ExportedObject(Bus* bus,
                  const std::string& service_name,
-                 const std::string& object_path);
+                 const ObjectPath& object_path);
 
   // Called to send a response from an exported method. Response* is the
   // response message. Callers should pass a NULL Response* in the event
@@ -157,7 +158,7 @@ class ExportedObject : public base::RefCountedThreadSafe<ExportedObject> {
 
   scoped_refptr<Bus> bus_;
   std::string service_name_;
-  std::string object_path_;
+  ObjectPath object_path_;
   bool object_is_registered_;
 
   // The method table where keys are absolute method names (i.e. interface