Fixed a leak in StringTraceDataSink following b47076f

content/browser/tracing/tracing_controller_impl.cc

Index: content/browser/tracing/tracing_controller_impl.cc
diff --git a/content/browser/tracing/tracing_controller_impl.cc b/content/browser/tracing/tracing_controller_impl.cc
index 680963a5e395bfaf80488f84a7f8d60d03b864a3..fbff7c9036923ac50dd36e1ac4392e169cd9df0d 100644
--- a/content/browser/tracing/tracing_controller_impl.cc
+++ b/content/browser/tracing/tracing_controller_impl.cc
@@ -135,7 +135,9 @@ class StringTraceDataSink : public TracingController::TraceDataSink {
       result += ",\"systemTraceEvents\": " + system_trace_;
     result += "}";
 
-    completion_callback_.Run(base::RefCountedString::TakeString(&result));
+    scoped_refptr<base::RefCountedString> str =
+        base::RefCountedString::TakeString(&result);
+    completion_callback_.Run(str.get());
   }
 
  private: