[Startup Tracing] Remove |is_recording_| in devtool tracing_handler

content/public/browser/tracing_controller.h

 // Copyright 2013 The Chromium 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 CONTENT_PUBLIC_BROWSER_TRACING_CONTROLLER_H_
 #define CONTENT_PUBLIC_BROWSER_TRACING_CONTROLLER_H_
 
 #include <set>
 #include <string>
 
@@ skipping 181 matching lines @@
   // process.
   typedef base::Callback<void()> WatchEventCallback;
   virtual bool SetWatchEvent(const std::string& category_name,
                              const std::string& event_name,
                              const WatchEventCallback& callback) = 0;
 
   // Cancel the watch event. If tracing is enabled, this may race with the
   // watch event callback.
   virtual bool CancelWatchEvent() = 0;
 
+  // Check if the tracing system is recording
+  virtual bool IsRecording() const = 0;
+
  protected:
   virtual ~TracingController() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_TRACING_CONTROLLER_H_