DevTools: respond with error when Debugger command is sent to disabled debugger agent

Source/core/inspector/InspectorDebuggerAgent.h

 /*
  * 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 194 matching lines @@
     virtual InjectedScript injectedScriptForEval(ErrorString*, const int* executionContextId) = 0;
 
     virtual void enable();
     virtual void disable();
     SkipPauseRequest didPause(ScriptState*, const ScriptValue& callFrames, const ScriptValue& exception, const Vector<String>& hitBreakpoints, bool isPromiseRejection) final;
     void didContinue() final;
     void reset();
     void resetModifiedSources();
 
 private:
+    bool checkEnabled(ErrorString*);
+
     SkipPauseRequest shouldSkipExceptionPause();
     SkipPauseRequest shouldSkipStepPause();
 
     void schedulePauseOnNextStatementIfSteppingInto();
     void cancelPauseOnNextStatement();
     void addMessageToConsole(MessageSource, MessageType);
 
     PassRefPtr<TypeBuilder::Array<TypeBuilder::Debugger::CallFrame> > currentCallFrames();
     PassRefPtr<TypeBuilder::Debugger::StackTrace> currentAsyncStackTrace();
 
@@ skipping 78 matching lines @@
     int m_currentAsyncOperationId;
     bool m_pendingTraceAsyncOperationCompleted;
     bool m_startingStepIntoAsync;
     WillBeHeapVector<RawPtrWillBeMember<AsyncCallTrackingListener>> m_asyncCallTrackingListeners;
 };
 
 } // namespace blink
 
 
 #endif // InspectorDebuggerAgent_h