Adds comments to BrowserList::GetLastActive that it might return NULL...

chrome/browser/browser_list.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_BROWSER_LIST_H__
 #define CHROME_BROWSER_BROWSER_LIST_H__
 
 #include <algorithm>
 #include <vector>
 
@@ skipping 30 matching lines @@
   static void AddObserver(Observer* observer);
   static void RemoveObserver(Observer* observer);
 
   // Called by Browser objects when their window is activated (focused).  This
   // allows us to determine what the last active Browser was.
   static void SetLastActive(Browser* browser);
 
   // Returns the Browser object whose window was most recently active.  If the
   // most recently open Browser's window was closed, returns the first Browser
   // in the list.  If no Browsers exist, returns NULL.
+  //
+  // WARNING: this is NULL until a browser becomes active. If during startup
+  // a browser does not become active (perhaps the user launches Chrome, then
+  // clicks on another app before the first browser window appears) then this
+  // returns NULL.
   static Browser* GetLastActive();
 
   // Identical in behavior to GetLastActive(), except that the most recently
   // open browser owned by |profile| is returned. If none exist, returns NULL.
   static Browser* GetLastActiveWithProfile(Profile *profile);
 
   // Find an existing browser window with the provided type. If the last active
   // has the right type, it is returned. Otherwise, the next available browser
   // is returned. Returns NULL if no such browser currently exists.
   static Browser* FindBrowserWithType(Profile* p, Browser::Type t);
@@ skipping 120 matching lines @@
   // tab index into the current Browser of the current web view
   int web_view_index_;
 
   // Current TabContents, or NULL if we're at the end of the list. This can
   // be extracted given the browser iterator and index, but it's nice to cache
   // this since the caller may access the current host many times.
   TabContents* cur_;
 };
 
 #endif  // CHROME_BROWSER_BROWSER_LIST_H__