Add support for writing system traces at startup

content/browser/tracing/trace_subscriber_stdio.h

Index: content/browser/tracing/trace_subscriber_stdio.h
diff --git a/content/browser/tracing/trace_subscriber_stdio.h b/content/browser/tracing/trace_subscriber_stdio.h
index 06a70db8c88be665ec5407aa1f3df7109cfd7bb3..610f8c8e4abd5455525b59184bf973f62c17603a 100644
--- a/content/browser/tracing/trace_subscriber_stdio.h
+++ b/content/browser/tracing/trace_subscriber_stdio.h
@@ -17,14 +17,18 @@ class FilePath;
 
 namespace content {
 
-class TraceSubscriberStdioImpl;
-
 // Stdio implementation of TraceSubscriber. Use this to write traces to a file.
 class CONTENT_EXPORT TraceSubscriberStdio
     : NON_EXPORTED_BASE(public TraceSubscriber) {
  public:
-  // Creates or overwrites the specified file. Check IsValid() for success.
-  explicit TraceSubscriberStdio(const base::FilePath& path);
+  enum FileType {

[sky, 2013/08/20 14:28:44]

Please add a description of what these mean.

[DaveMoore, 2013/08/20 14:58:00]

Done.

+    FILE_TYPE_ARRAY,
+    FILE_TYPE_PROPERTY_LIST
+  };
+
+  TraceSubscriberStdio(const base::FilePath& path,
+                       FileType file_type,
+                       bool has_system_trace);

[sky, 2013/08/20 14:28:44]

Add a description for has_system_trace.

[DaveMoore, 2013/08/20 14:58:00]

Done.

   virtual ~TraceSubscriberStdio();
 
   // Implementation of TraceSubscriber
@@ -32,8 +36,12 @@ class CONTENT_EXPORT TraceSubscriberStdio
   virtual void OnTraceDataCollected(
       const scoped_refptr<base::RefCountedString>& data_ptr) OVERRIDE;
 
+  virtual void OnEndSystemTracing(

[sky, 2013/08/20 14:36:09]

One more. Is this part of TraceSubscriber? If so, remove 38 and add OVERRIDE. If
not, does it need to be public and virtual? Also, please document it (assuming
it isn't an OVERRIDE).

[DaveMoore, 2013/08/20 14:58:00]

Done.

+    const scoped_refptr<base::RefCountedString>& events_str_ptr);

[sky, 2013/08/20 14:36:09]

nit: two more spaces here.

[DaveMoore, 2013/08/20 14:58:00]

Done.

+
  private:
-  scoped_refptr<TraceSubscriberStdioImpl> impl_;
+  class TraceSubscriberStdioWorker;
+  scoped_refptr<TraceSubscriberStdioWorker> worker_;
   DISALLOW_COPY_AND_ASSIGN(TraceSubscriberStdio);
 };