Revert of Add EnabledStateObserver to BackgroundTracingManager

content/public/browser/background_tracing_manager.h

 // Copyright 2015 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_BACKGROUND_TRACING_MANAGER_H_
 #define CONTENT_PUBLIC_BROWSER_BACKGROUND_TRACING_MANAGER_H_
 
 #include <memory>
 
 #include "base/trace_event/trace_event_impl.h"
@@ skipping 75 matching lines @@
       TriggerHandle trigger_handle,
       StartedFinalizingCallback started_callback) = 0;
 
   // Registers a manual trigger handle, and returns a TriggerHandle which can
   // be passed to DidTriggerHappen().
   virtual TriggerHandle RegisterTriggerType(const char* trigger_name) = 0;
 
   virtual bool HasActiveScenario() = 0;
 
   virtual void InvalidateTriggerHandlesForTesting() = 0;
+  virtual void SetTracingEnabledCallbackForTesting(
+      const base::Closure& callback) = 0;
   virtual void FireTimerForTesting() = 0;
 
  protected:
   virtual ~BackgroundTracingManager() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_BACKGROUND_TRACING_MANAGER_H_