Make BrowserList::(Add|Remove)Observer add the observer to every desktop's browser list.

chrome/browser/ui/browser_list.h

Index: chrome/browser/ui/browser_list.h
diff --git a/chrome/browser/ui/browser_list.h b/chrome/browser/ui/browser_list.h
index f3103cf81e96af75cc13c59cac3cae348478cef5..eb48b2fd9ab4826fdff44375d699ebcc5e3c6eec 100644
--- a/chrome/browser/ui/browser_list.h
+++ b/chrome/browser/ui/browser_list.h
@@ -22,12 +22,13 @@ class BrowserList {
   typedef std::vector<Browser*> BrowserVector;
   typedef BrowserVector::const_reverse_iterator const_reverse_iterator;
 
-  // Adds and removes browsers from the global list. The browser object should
-  // be valid BEFORE these calls (for the benefit of observers), so notify and
-  // THEN delete the object.
+  // Adds and removes browsers from the list they are associated with. The
+  // browser object should be valid BEFORE these calls (for the benefit of
+  // observers), so notify and THEN delete the object.
   static void AddBrowser(Browser* browser);
   static void RemoveBrowser(Browser* browser);
 
+  // Adds and removes |observer| from the observer list of each desktop.
   static void AddObserver(chrome::BrowserListObserver* observer);
   static void RemoveObserver(chrome::BrowserListObserver* observer);