QmlProfiler: flush on new trace

Discard pending data if a new trace arrives while an old one
was still being processed.  If we don't, the data of both
traces gets mixed, leading to a possible crash.

Change-Id: Ibba7df06f6a4b7e93d00f6fa1fa4802baf3a1731
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>

src/plugins/qmlprofiler/qmlprofilerclientmanager.h

@@ -55,6 +55,7 @@ public:
     void setOstConnection(QString ostDevice);
 
     void clearBufferedData();
+    void discardPendingData();
 
 signals:
     void connectionFailed();