Add a |scope| argument to TRACE_EVENT_INSTANT* and require its presence.

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index 4b7feb67d70df9371021f08e7a97e246394b5c21..e85329f094413a61e3543c23ff73123a40a7af3c 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -749,7 +749,8 @@ void BrowserMainLoop::BrowserThreadsStarted() {
       !parsed_command_line_.HasSwitch(switches::kDisableGpuProcessPrelaunch) &&
       !parsed_command_line_.HasSwitch(switches::kSingleProcess) &&
       !parsed_command_line_.HasSwitch(switches::kInProcessGPU)) {
-    TRACE_EVENT_INSTANT0("gpu", "Post task to launch GPU process");
+    TRACE_EVENT_INSTANT0("gpu", "Post task to launch GPU process",
+                         TRACE_EVENT_SCOPE_THREAD);
     BrowserThread::PostTask(
         BrowserThread::IO, FROM_HERE, base::Bind(
             base::IgnoreResult(&GpuProcessHost::Get),