Inspector: replace generic discardAgents logic with explicit call to discard a listener.

Source/core/inspector/InspectorDebuggerAgent.cpp

Index: Source/core/inspector/InspectorDebuggerAgent.cpp
diff --git a/Source/core/inspector/InspectorDebuggerAgent.cpp b/Source/core/inspector/InspectorDebuggerAgent.cpp
index b4e9a0259f1dc7ff5b89f29bd2d802e4c32ce0a7..e23971638143616e3c9866e0b815165d0a8db98a 100644
--- a/Source/core/inspector/InspectorDebuggerAgent.cpp
+++ b/Source/core/inspector/InspectorDebuggerAgent.cpp
@@ -84,6 +84,8 @@ InspectorDebuggerAgent::InspectorDebuggerAgent(InstrumentingAgents* instrumentin
 
 InspectorDebuggerAgent::~InspectorDebuggerAgent()
 {
+    if (m_listener)
+        m_listener->discardListener();
     ASSERT(!m_instrumentingAgents->inspectorDebuggerAgent());
 }