Revert of Revert "Revert 237280 "Remove TraceController""

content/public/browser/trace_subscriber.h

Index: content/public/browser/trace_subscriber.h
diff --git a/content/public/browser/trace_subscriber.h b/content/public/browser/trace_subscriber.h
new file mode 100644
index 0000000000000000000000000000000000000000..8b63d3588e80d81d56c20f123d9fa63d8f39906d
--- /dev/null
+++ b/content/public/browser/trace_subscriber.h
@@ -0,0 +1,43 @@
+// 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_