Add EnabledStateObserver to BackgroundTracingManager

content/browser/tracing/background_memory_tracing_observer.h

Index: content/browser/tracing/background_memory_tracing_observer.h
diff --git a/content/browser/tracing/background_memory_tracing_observer.h b/content/browser/tracing/background_memory_tracing_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..abd7e92d8de2f2cab8123582f3ab8168395a64c2
--- /dev/null
+++ b/content/browser/tracing/background_memory_tracing_observer.h
@@ -0,0 +1,30 @@
+// Copyright 2017 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_BROWSER_TRACING_BACKGROUND_MEMORY_TRACING_OBSERVER_H_
+#define CONTENT_BROWSER_TRACING_BACKGROUND_MEMORY_TRACING_OBSERVER_H_
+
+#include "content/browser/tracing/background_tracing_manager_impl.h"
+
+namespace content {
+
+class BackgroundMemoryTracingObserver
+    : public BackgroundTracingManagerImpl::EnabledStateObserver {
+ public:
+  static BackgroundMemoryTracingObserver* GetInstance();
+
+  void OnScenarioActivated(const BackgroundTracingConfigImpl& config) override;
+  void OnTracingEnabled(
+      BackgroundTracingConfigImpl::CategoryPreset preset) override;
+
+ private:
+  BackgroundMemoryTracingObserver();
+  ~BackgroundMemoryTracingObserver() override;
+
+  DISALLOW_COPY_AND_ASSIGN(BackgroundMemoryTracingObserver);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_TRACING_BACKGROUND_MEMORY_TRACING_OBSERVER_H_