Revert "Revert 237280 "Remove TraceController""

content/public/browser/trace_subscriber.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_SUBSCRIBER_H_
-#define CONTENT_PUBLIC_BROWSER_TRACE_SUBSCRIBER_H_
-
-#include <set>
-
-#include "base/memory/ref_counted_memory.h"
-
-namespace content {
-
-// Objects interested in receiving trace data derive from TraceSubscriber. All
-// callbacks occur on the UI thread.
-// See also: trace_message_filter.h
-// See also: child_trace_message_filter.h
-class TraceSubscriber {
- public:
-  // Called once after TraceController::EndTracingAsync.
-  virtual void OnEndTracingComplete() {}
-
-  // Called 0 or more times between TraceController::BeginTracing and
-  // OnEndTracingComplete. Use base::debug::TraceResultBuffer to convert one or
-  // more trace fragments to JSON.
-  virtual void OnTraceDataCollected(
-      const scoped_refptr<base::RefCountedString>& trace_fragment) = 0;
-
-  // Called once after TraceController::GetKnownCategoryGroupsAsync.
-  virtual void OnKnownCategoriesCollected(
-      const std::set<std::string>& known_categories) {}
-
-  virtual void OnTraceBufferPercentFullReply(float percent_full) {}
-
-  virtual void OnEventWatchNotification() {}
-
- protected:
-  virtual ~TraceSubscriber() {}
-};
-
-}  // namespace content
-
-#endif  // CONTENT_PUBLIC_BROWSER_TRACE_SUBSCRIBER_H_