Add support for TraceEvent before the native library is loaded.

content/browser/tracing/tracing_controller_impl.h

Index: content/browser/tracing/tracing_controller_impl.h
diff --git a/content/browser/tracing/tracing_controller_impl.h b/content/browser/tracing/tracing_controller_impl.h
index a5563a8547ce9057fc9d1b331881cf67f7a4c859..b8b99bee23ec4d6c08618ae12649b564464ec3ac 100644
--- a/content/browser/tracing/tracing_controller_impl.h
+++ b/content/browser/tracing/tracing_controller_impl.h
@@ -9,6 +9,8 @@
 #include <string>
 #include <vector>
 
+#include "base/callback.h"
+#include "base/files/file_path.h"
 #include "base/lazy_instance.h"
 #include "content/public/browser/tracing_controller.h"
 
@@ -24,6 +26,9 @@ class TracingUI;
 
 class TracingControllerImpl : public TracingController {
  public:
+  typedef base::Callback<
+      void (base::trace_event::TraceLog*)> DisableRecordingCallback;
+
   static TracingControllerImpl* GetInstance();
 
   // TracingController implementation.
@@ -54,6 +59,8 @@ class TracingControllerImpl : public TracingController {
   void RegisterTracingUI(TracingUI* tracing_ui);
   void UnregisterTracingUI(TracingUI* tracing_ui);
 
+  void SetDisableRecordingCallback(const DisableRecordingCallback& callback);
+
  private:
   typedef std::set<scoped_refptr<TraceMessageFilter> > TraceMessageFilterSet;
 
@@ -173,6 +180,8 @@ class TracingControllerImpl : public TracingController {
   std::set<TracingUI*> tracing_uis_;
   scoped_refptr<TraceDataSink> trace_data_sink_;
   scoped_refptr<TraceDataSink> monitoring_data_sink_;
+  DisableRecordingCallback disable_recording_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(TracingControllerImpl);
 };