Plumb NotifierId to status icon balloons

chrome/browser/status_icons/status_icon.h

Index: chrome/browser/status_icons/status_icon.h
diff --git a/chrome/browser/status_icons/status_icon.h b/chrome/browser/status_icons/status_icon.h
index 4f35abc56ce290ce240b1a7838a1f17add405cb5..e49c9984dd4a70cc4a20a2b42ff039badd1dfb28 100644
--- a/chrome/browser/status_icons/status_icon.h
+++ b/chrome/browser/status_icons/status_icon.h
@@ -15,6 +15,10 @@ namespace gfx {
 class ImageSkia;
 }
 
+namespace message_center {
+struct NotifierId;
+}
+
 class StatusIconObserver;
 
 class StatusIcon {
@@ -33,9 +37,11 @@ class StatusIcon {
 
   // Displays a notification balloon with the specified contents.
   // Depending on the platform it might not appear by the icon tray.
-  virtual void DisplayBalloon(const gfx::ImageSkia& icon,
-                              const base::string16& title,
-                              const base::string16& contents) = 0;
+  virtual void DisplayBalloon(
+      const gfx::ImageSkia& icon,
+      const base::string16& title,
+      const base::string16& contents,
+      const message_center::NotifierId& notifier_id) = 0;

[Peter Beverloo, 2015/10/10 16:35:27]

I'm a bit torn on what type to use here.

Yes, mc::NotifierId certainly is applicable since that's what it will be used
as, but it's entirely unrelated to what any platform-native (e.g. Windows)
implementation would be using, unless you think of it strictly as a data
carrier.

On the other end, using something like "const char* source" is not super obvious
either, and would require one to read this comment (when amended) for context.

I don't feel strongly one way or another, but perhaps Justin or Andrew will have
an opinion.

[johnme, 2015/10/12 14:34:09]

Since this is a method for displaying "a notification balloon", it doesn't seem
unreasonable for it to always take a NotifierId, even on platforms where it uses
a native balloon rather than Chrome's notifications.

 
   // Set the context menu for this icon. The icon takes ownership of the passed
   // context menu. Passing NULL results in no menu at all.