Allow TracingController to output trace data to specified file

content/public/browser/tracing_controller.h

Index: content/public/browser/tracing_controller.h
diff --git a/content/public/browser/tracing_controller.h b/content/public/browser/tracing_controller.h
index d3bc7bd9df9f2ec6dc5cbd6d305d6dacaec1e070..2434ad4967a2ec64f0ac2a54b763fe13efa20155 100644
--- a/content/public/browser/tracing_controller.h
+++ b/content/public/browser/tracing_controller.h
@@ -75,9 +75,16 @@ class TracingController {
   // 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.
   //
@@ -119,7 +126,14 @@ class TracingController {
   // 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: