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

Source/core/inspector/InspectorDebuggerAgent.cpp

 /*
  * Copyright (C) 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010-2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 66 matching lines @@
     , m_javaScriptPauseScheduled(false)
     , m_listener(0)
 {
     // FIXME: make breakReason optional so that there was no need to init it with "other".
     clearBreakDetails();
     m_state->setLong(DebuggerAgentState::pauseOnExceptionsState, ScriptDebugServer::DontPauseOnExceptions);
 }
 
 InspectorDebuggerAgent::~InspectorDebuggerAgent()
 {
+    if (m_listener)
+        m_listener->willDestroyDebuggerAgent();
     ASSERT(!m_instrumentingAgents->inspectorDebuggerAgent());
 }
 
 void InspectorDebuggerAgent::enable()
 {
     m_instrumentingAgents->setInspectorDebuggerAgent(this);
 
     // FIXME(WK44513): breakpoints activated flag should be synchronized between all front-ends
     scriptDebugServer().setBreakpointsActivated(true);
     startListeningScriptDebugServer();
@@ skipping 746 matching lines @@
 void InspectorDebuggerAgent::reset()
 {
     m_scripts.clear();
     m_breakpointIdToDebugServerBreakpointIds.clear();
     if (m_frontend)
         m_frontend->globalObjectCleared();
 }
 
 } // namespace WebCore