Provide a better way of injecting extra diagnostics in feedbacks

chrome/browser/chromeos/login/ui/login_feedback.cc

Index: chrome/browser/chromeos/login/ui/login_feedback.cc
diff --git a/chrome/browser/chromeos/login/ui/login_feedback.cc b/chrome/browser/chromeos/login/ui/login_feedback.cc
index 6b216dff3dbd71ec152d2f6dd54e497dc134c1f0..5c6dd7b0b0c0ded0c8d1ab6fb529c0e7197f6801 100644
--- a/chrome/browser/chromeos/login/ui/login_feedback.cc
+++ b/chrome/browser/chromeos/login/ui/login_feedback.cc
@@ -253,7 +253,7 @@ void LoginFeedback::EnsureFeedbackUI() {
   extensions::FeedbackPrivateAPI* api =
       extensions::FeedbackPrivateAPI::GetFactoryInstance()->Get(profile_);
   api->RequestFeedbackForFlow(
-      description_, "Login", GURL(),
+      description_, "Login", std::string() /* extra_diagnostics */, GURL(),

[Peter Kasting, 2017/06/14 20:41:04]

Nit: While there's no formal rule up or down on these sorts of comments, I'm not
generally a fan of inserting them if existing code isn't already using them. 
They call attention to the arg when, often, the reader doesn't need to be
thinking about that arg; and it's generally easy to find param names in the
IDE/codesearch.  There's a number of places in this CL that do this; up to you
what to do with this feedback.

[afakhry, 2017/06/14 22:10:18]

I kept them only in the code that was already using them, and removed them from
the code that doesn't.

       extensions::api::feedback_private::FeedbackFlow::FEEDBACK_FLOW_LOGIN);
 
   // Make sure there is a feedback app window opened.