implement SetWatchEvent and WaitForEvent for trace-based-tests

content/public/browser/trace_controller.h

 // Copyright (c) 2012 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_TRACE_CONTROLLER_H_
 #define CONTENT_PUBLIC_BROWSER_TRACE_CONTROLLER_H_
 
 #include "content/common/content_export.h"
 
 namespace content {
@@ skipping 50 matching lines @@
   // When the TraceBufferPercentFull value is determined,
   // subscriber->OnTraceBufferPercentFullReply is called.
   // When any child process reaches 100% full, the TraceController will end
   // tracing, and call TraceSubscriber::OnEndTracingComplete.
   // GetTraceBufferPercentFullAsync fails in the following conditions:
   //   trace is ending or disabled;
   //   a previous call to GetTraceBufferPercentFullAsync is pending; or
   //   the caller is not the current subscriber.
   virtual bool GetTraceBufferPercentFullAsync(TraceSubscriber* subscriber) = 0;
 
+  // |subscriber->OnEventWatchNotification()| will be called every time the
+  // given event occurs on any process.
+  virtual bool SetWatchEvent(TraceSubscriber* subscriber,
+                             const std::string& category_name,
+                             const std::string& event_name) = 0;
+
+  // Cancel the watch event. If tracing is enabled, this may race with the
+  // watch event notification firing.
+  virtual bool CancelWatchEvent(TraceSubscriber* subscriber) = 0;
+
   // Cancel the subscriber so that it will not be called when EndTracingAsync is
   // acked by all child processes. This will also call EndTracingAsync
   // internally if necessary.
   // Safe to call even if caller is not the current subscriber.
   virtual void CancelSubscriber(TraceSubscriber* subscriber) = 0;
 
  protected:
   virtual ~TraceController() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_TRACE_CONTROLLER_H_