Set new homepage preferences only if there is no existing value.

chrome/browser/browser.h

 // Copyright (c) 2006-2009 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_H_
 #define CHROME_BROWSER_BROWSER_H_
 
 #include <map>
 #include <set>
 #include <vector>
@@ skipping 390 matching lines @@
 #if defined(OS_CHROMEOS)
   void ShowControlPanel();
 #endif
 
   virtual void UpdateDownloadShelfVisibility(bool visible);
 
   /////////////////////////////////////////////////////////////////////////////
 
   // Sets the value of homepage related prefs to new values. Since we do not
   // want to change these values for existing users, we can not change the
-  // default values under RegisterUserPrefs. This method gets called during
-  // First Run.
+  // default values under RegisterUserPrefs. Also if user already has an
+  // existing profile we do not want to override those preferences so we only
+  // set new values if they have not been set already. This method gets called
+  // during First Run.
   static void SetNewHomePagePrefs(PrefService* prefs);
 
   static void RegisterPrefs(PrefService* prefs);
   static void RegisterUserPrefs(PrefService* prefs);
 
   // Returns the Browser which contains the tab with the given
   // NavigationController, also filling in |index| (if valid) with the tab's
   // index in the tab strip.
   // Returns NULL if not found.
   // This call is O(N) in the number of tabs.
@@ skipping 373 matching lines @@
   // The browser idle task helps cleanup unused memory resources when idle.
   scoped_ptr<BrowserIdleTimer> idle_task_;
 
   // Keep track of the encoding auto detect pref.
   BooleanPrefMember encoding_auto_detect_;
 
   DISALLOW_COPY_AND_ASSIGN(Browser);
 };
 
 #endif  // CHROME_BROWSER_BROWSER_H_