Make NotificationFrame::getSubject const

Author: mkochenough

src/websocket.cc

@@ -104,7 +104,7 @@ NotificationFrame::~NotificationFrame() {
 }
 
 string
-NotificationFrame::getSubject() {
+NotificationFrame::getSubject() const {
   string type("Unknown notification type");
   string dataStr(mData, mDataLength);
   int posStart = dataStr.find("\"type\":\"");

src/websocket.h

@@ -49,7 +49,7 @@ class NotificationFrame : public WebSocketFrame
   NotificationFrame(int flags);
   virtual ~NotificationFrame();
 
-  virtual string getSubject();
+  virtual string getSubject() const;
   virtual void setSubject(string subject);
 };