DevTools: handle Tracing.start in both browser and renderer

content/browser/devtools/devtools_tracing_handler.cc

Index: content/browser/devtools/devtools_tracing_handler.cc
diff --git a/content/browser/devtools/devtools_tracing_handler.cc b/content/browser/devtools/devtools_tracing_handler.cc
index 5e97b1b69343cf4c83967507b6d678948869ea64..ffe02c1df26c33545bdfe0ae1fbc7440b7ed46db 100644
--- a/content/browser/devtools/devtools_tracing_handler.cc
+++ b/content/browser/devtools/devtools_tracing_handler.cc
@@ -169,17 +169,9 @@ DevToolsTracingHandler::OnStart(
   }
 
   TracingController::GetInstance()->EnableRecording(
-      categories, options,
-      base::Bind(&DevToolsTracingHandler::OnTracingStarted,
-                 weak_factory_.GetWeakPtr(),
-                 command));
+      categories, options, TracingController::EnableRecordingDoneCallback());
 
-  return command->AsyncResponsePromise();
-}
-
-void DevToolsTracingHandler::OnTracingStarted(
-    scoped_refptr<DevToolsProtocol::Command> command) {
-  SendAsyncResponse(command->SuccessResponse(NULL));
+  return NULL;
 }
 
 void DevToolsTracingHandler::OnBufferUsage(float usage) {