Add trace events in NavigationControllerImpl::back/forward(...).

content/browser/frame_host/navigation_controller_impl.cc

Index: content/browser/frame_host/navigation_controller_impl.cc
diff --git a/content/browser/frame_host/navigation_controller_impl.cc b/content/browser/frame_host/navigation_controller_impl.cc
index 7e04526e5894a53823c197cb54cff0163ebfacc4..cc647ac174045066482b9189a272aeaa487a86da 100644
--- a/content/browser/frame_host/navigation_controller_impl.cc
+++ b/content/browser/frame_host/navigation_controller_impl.cc
@@ -587,11 +587,15 @@ bool NavigationControllerImpl::CanGoToOffset(int offset) const {
 
 void NavigationControllerImpl::GoBack() {
   // Call GoToIndex rather than GoToOffset to get the NOTREACHED() check.

[tdresser, 2017/03/16 12:24:38]

Move the comment below the trace event, it's referring to the GoToIndex call.
(And below)

[sunjian, 2017/03/16 18:40:30]

Acknowledged.

+  TRACE_EVENT0("browser,navigation",
+               "NavigationControllerImpl::GoBack");
   GoToIndex(GetIndexForOffset(-1));
 }
 
 void NavigationControllerImpl::GoForward() {
   // Call GoToIndex rather than GoToOffset to get the NOTREACHED() check.
+  TRACE_EVENT0("browser,navigation",
+               "NavigationControllerImpl::GoForward");
   GoToIndex(GetIndexForOffset(1));
 }