Add pref to enable/disable palette tray.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 56c03f4ea5bbeb0aebec2dfc8796890795ed0312..37b44c379dae9233631f417a68270107023293a3 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -674,6 +674,9 @@ const char kSecondaryDisplays[] = "settings.display.secondary_displays";
 // display orientation, for the internal display.
 const char kDisplayRotationLock[] = "settings.display.rotation_lock";
 
+// A boolean pref that specifies if the stylus tools should be enabled/disabled.
+const char kEnableStylusTools[] = "settings.enable_stylus_tools";
+
 // A boolean pref that specifies if the ash palette should be launched after an
 // eject input event has been received.
 const char kLaunchPaletteOnEjectEvent[] =