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 6eeb338155415001d6aa5c6beb459068ca679891..bcb17626ad4764743df580c07f05afc1d7b813f5 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -670,6 +670,9 @@ 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 ash palette should be enabled/disabled.
+const char kEnableAshPalette[] = "settings.enable_ash_palette";
+
 // A boolean pref that specifies if the default note-taking app should be
 // launched after an eject input event has been received.
 const char kLaunchNoteAppOnEjectEvent[] =