Allow TracingController to output trace data to specified file

content/public/browser/tracing_controller.h

 // Copyright 2013 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_TRACING_CONTROLLER_H_
 #define CONTENT_PUBLIC_BROWSER_TRACING_CONTROLLER_H_
 
 #include "base/debug/trace_event.h"
 #include "content/common/content_export.h"
 
@@ skipping 57 matching lines @@
   //
   // 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 to the DisableRecording request,
   // TracingFileResultCallback will be called back with a file that contains
   // the traced data.
-  typedef base::Callback<void(scoped_ptr<base::FilePath>)>
-      TracingFileResultCallback;
-  virtual bool DisableRecording(const TracingFileResultCallback& callback) = 0;
+  //
+  // Trace data will be written into |result_file_path| if it is not empty, or
+  // into a temporary file. The actual file path will be passed to |callback| if

[Jói, 2013/11/19 12:42:22]

into a temporary file -> into the previously set file (?)

+  // it's not null.
+  //
+  // If |result_file_path| is empty and |callback| is null, trace data won't be

[Jói, 2013/11/19 12:42:22]

This doesn't look like it's quite accurate for this function; result_file_ is
reset only if either |callback| is not null or |result_file_path| is not empty.
In other cases it will be written to |result_file_path| or a temp file if that
is empty.

[Xianzhu, 2013/11/19 16:48:34]

result_file_ will be reset to NULL when the whole DisableRecording() process
finishes (in OnResultFileClosed). DisableRecording() will return false directly
if there is no recording or the last DisableRecording() has not finished. So
every time DisableRecording() doesn't return false, ResultFile is always a new
object and will create temporary file if |result_file_path| is empty.

Changed can_disable_recording to make the logic more explicit.

+  // written to any file.
+  typedef base::Callback<void(const base::FilePath&)> TracingFileResultCallback;
+  virtual bool DisableRecording(const base::FilePath& result_file_path,
+                                const TracingFileResultCallback& callback) = 0;
 
   // Start monitoring on all processes.
   //
   // Monitoring begins immediately locally, and asynchronously on child
   // processes as soon as they receive the EnableMonitoring request.
   //
   // Once all child processes have acked to the EnableMonitoring request,
   // EnableMonitoringDoneCallback will be called back.
   //
   // |filter| is a filter to control what category groups should be traced.
@@ skipping 21 matching lines @@
   //
   // 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 to the CaptureMonitoringSnapshot
   // request, TracingFileResultCallback will be called back with a file that
   // contains the traced data.
+  //
+  // Trace data will be written into |result_file_path| if it is not empty, or
+  // into a temporary file. The actual file path will be passed to |callback|.
+  //
+  // If |result_file_path| is empty and |callback| is null, trace data won't be
+  // written to any file.
   virtual void CaptureMonitoringSnapshot(
+      const base::FilePath& result_file_path,
       const TracingFileResultCallback& callback) = 0;
 
  protected:
   virtual ~TracingController() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_TRACING_CONTROLLER_H_