Add ApiActivityMonitor to decouple ActivityLog from low-level extensions code

extensions/browser/api_activity_monitor.h

Index: extensions/browser/api_activity_monitor.h
diff --git a/extensions/browser/api_activity_monitor.h b/extensions/browser/api_activity_monitor.h
new file mode 100644
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+++ b/extensions/browser/api_activity_monitor.h
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+// Copyright 2014 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 EXTENSIONS_BROWSER_API_ACTIVITY_MONITOR_H_
+#define EXTENSIONS_BROWSER_API_ACTIVITY_MONITOR_H_
+
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+
+namespace base {
+class ListValue;
+}
+
+namespace extensions {
+
+// ApiActivityMonitor is used to monitor extension API event dispatch and API
+// function calls. An embedder can use this interface to log low-level extension
+// activity.
+class ApiActivityMonitor {
+ public:
+  // Called when an API event is dispatched to an extension.
+  virtual void OnApiEventDispatched(const std::string& extension_id,
+                                    const std::string& event_name,
+                                    scoped_ptr<base::ListValue> event_args) = 0;
+
+  // Called when an extension calls an API function.
+  virtual void OnApiFunctionCalled(const std::string& extension_id,
+                                   const std::string& api_name,
+                                   scoped_ptr<base::ListValue> args) = 0;
+
+ protected:
+  virtual ~ApiActivityMonitor() {}
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_API_ACTIVITY_MONITOR_H_