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..d4d54880d450819930a1c05b71a3ffbe6a31469c 100644
--- a/content/public/browser/tracing_controller.h
+++ b/content/public/browser/tracing_controller.h
@@ -75,9 +75,15 @@ 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 |result_file_path| is empty and |callback| is null, trace data won't be

[dsinclair, 2013/11/18 16:32:18]

Isn't this an OR instead of an AND.

[Xianzhu, 2013/11/18 21:50:39]

Used 'AND' because I thought the following might be a useful case: the caller
wants to save the traces into a file but don't care when the async process
finishes. The current impl is following the comment here.

[Xianzhu, 2013/11/18 21:56:09]

Note this is also consistent with other methods that will do the actual thing
(if it's meaningful) when the callback is null.

+  // 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 +125,14 @@ 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: