Add QObject constructor.

(cherry picked from commit 3f0c779308cfa5cca5193c740d3057a23ddcec25)

src/core/macfslistener.h

@@ -10,7 +10,7 @@ class MacFSListener : public QObject {
   Q_OBJECT
 
  public:
-  MacFSListener();
+  explicit MacFSListener(QObject* parent = 0);
   void Init();
 
   void AddPath(const QString& path);

src/core/macfslistener.mm

@@ -6,8 +6,9 @@
 
 #include "core/logging.h"
 
-MacFSListener::MacFSListener()
-    : run_loop_(NULL),
+MacFSListener::MacFSListener(QObject* parent)
+    : QObject(parent),
+      run_loop_(NULL),
       stream_(NULL) {
 }