Allow use of the chrome trace categories string from the tracing ui internals.

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 {
 
 class TraceSubscriber;
 
 // TraceController is used on the browser processes to enable/disable
 // trace status and collect trace data. Only the browser UI thread is allowed
 // to interact with the TraceController object. All calls on the TraceSubscriber
 // happen on the UI thread.
 class TraceController {
  public:
   CONTENT_EXPORT static TraceController* GetInstance();
 
   // Called by browser process to start tracing events on all processes.
   //
   // Currently only one subscriber is allowed at a time.
   // Tracing begins immediately locally, and asynchronously on child processes
   // as soon as they receive the BeginTracing request.
-  // By default, all categories are traced except those matching "test_*".
   //
   // 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.
-  virtual bool BeginTracing(TraceSubscriber* subscriber) = 0;
-
+  //
   // |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.
   //
   // 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;
@@ skipping 32 matching lines @@
   virtual void CancelSubscriber(TraceSubscriber* subscriber) = 0;
 
  protected:
   virtual ~TraceController() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_TRACE_CONTROLLER_H_