[inspector] avoid cloning of async call chains

src/inspector/v8-debugger-agent-impl.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_INSPECTOR_V8DEBUGGERAGENTIMPL_H_
 #define V8_INSPECTOR_V8DEBUGGERAGENTIMPL_H_
 
 #include <vector>
 
 #include "src/base/macros.h"
 #include "src/debug/interface-types.h"
 #include "src/inspector/java-script-call-frame.h"
 #include "src/inspector/protocol/Debugger.h"
 #include "src/inspector/protocol/Forward.h"
 
 namespace v8_inspector {
 
 struct ScriptBreakpoint;
 class JavaScriptCallFrame;
 class PromiseTracker;
 class V8Debugger;
 class V8DebuggerScript;
 class V8InspectorImpl;
 class V8InspectorSessionImpl;
 class V8Regex;
-class V8StackTraceImpl;
 
 using protocol::Maybe;
 using protocol::Response;
 
 class V8DebuggerAgentImpl : public protocol::Debugger::Backend {
  public:
   enum BreakpointSource {
     UserBreakpointSource,
     DebugCommandBreakpointSource,
     MonitorCommandBreakpointSource
@@ skipping 164 matching lines @@
   std::unique_ptr<V8Regex> m_blackboxPattern;
   protocol::HashMap<String16, std::vector<std::pair<int, int>>>
       m_blackboxedPositions;
 
   DISALLOW_COPY_AND_ASSIGN(V8DebuggerAgentImpl);
 };
 
 }  // namespace v8_inspector
 
 #endif  // V8_INSPECTOR_V8DEBUGGERAGENTIMPL_H_