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

chrome/browser/browser.h

Index: chrome/browser/browser.h
diff --git a/chrome/browser/browser.h b/chrome/browser/browser.h
index 8ec55578e744fb0ac3b33ab94a1e2e8b243a7f74..8e42694eb545d494f241c479c5a45bf948a090a7 100644
--- a/chrome/browser/browser.h
+++ b/chrome/browser/browser.h
@@ -408,8 +408,10 @@ class Browser : public TabStripModelDelegate,
 
   // 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);