Re-land issue 750183008 (Parallelize trace messages serialization)

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 480481fdb74b1151f55269cdc6324f1766721e49..1622819b04d21abeb2eb3af9fad223cd07e92375 100644
--- a/content/browser/tracing/tracing_controller_impl.cc
+++ b/content/browser/tracing/tracing_controller_impl.cc
@@ -349,7 +349,8 @@ void TracingControllerImpl::OnDisableRecordingDone() {
     // Flush asynchronously now, because we don't have any children to wait for.
     TraceLog::GetInstance()->Flush(
         base::Bind(&TracingControllerImpl::OnLocalTraceDataCollected,
-                   base::Unretained(this)));
+                   base::Unretained(this)),
+        true);
   }
 
   // Notify all child processes.
@@ -682,7 +683,8 @@ void TracingControllerImpl::OnDisableRecordingAcked(
     // called with the last of the local trace data.
     TraceLog::GetInstance()->Flush(
         base::Bind(&TracingControllerImpl::OnLocalTraceDataCollected,
-                   base::Unretained(this)));
+                   base::Unretained(this)),
+        true);
     return;
   }