Remove balloon notification code. The last user was the Linux GTK port but that's deleted now.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
===================================================================
--- chrome/common/pref_names.cc	(revision 263121)
+++ chrome/common/pref_names.cc	(working copy)
@@ -1029,10 +1029,6 @@
 // true, we draw a custom chrome frame (thicker title bar and blue border).
 const char kUseCustomChromeFrame[] = "browser.custom_chrome_frame";
 
-// The preferred position (which corner of screen) for desktop notifications.
-const char kDesktopNotificationPosition[] =
-    "browser.desktop_notification_position";
-
 // Dictionary of content settings applied to all hosts by default.
 const char kDefaultContentSettings[] = "profile.default_content_settings";