Update tracing framework to optionally use a ringbuffer.

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 17 matching lines @@
   // If BeginTracing was already called previously,
   //   or if an EndTracingAsync is pending,
   //   or if another subscriber is tracing,
   //   BeginTracing will return false meaning it failed.
   //
   // |categories| is a comma-delimited list of category wildcards.
   // A category can have an optional '-' prefix to make it an excluded category.
   // All the same rules apply above, so for example, having both included and
   // excluded categories in the same list would not be supported.
   //
+  // |continuous_tracing| should be set to true to loop to the beginning of
+  // the trace buffer and continue tracing when the buffer is full.
+  //
   // Example: BeginTracing("test_MyTest*");
   // Example: BeginTracing("test_MyTest*,test_OtherStuff");
   // Example: BeginTracing("-excluded_category1,-excluded_category2");
   virtual bool BeginTracing(TraceSubscriber* subscriber,
                             const std::string& categories) = 0;
 
+  virtual bool BeginTracing(TraceSubscriber* subscriber,
+                            const std::string& categories,
+                            bool continuous_tracing) = 0;
+
   // Called by browser process to stop tracing events on all processes.
   //
   // Child processes typically are caching trace data and only rarely flush
   // and send trace data back to the browser process. That is because it may be
   // an expensive operation to send the trace data over IPC, and we would like
   // to avoid much runtime overhead of tracing. So, to end tracing, we must
   // asynchronously ask all child processes to flush any pending trace data.
   //
   // Once all child processes have acked the EndTracing request,
   // TraceSubscriber will be called with OnEndTracingComplete.
@@ skipping 31 matching lines @@
   virtual void CancelSubscriber(TraceSubscriber* subscriber) = 0;
 
  protected:
   virtual ~TraceController() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_TRACE_CONTROLLER_H_