Use multi-value switch to enable/disable the unified gesture detector.

ui/events/event_switches.cc

Index: ui/events/event_switches.cc
diff --git a/ui/events/event_switches.cc b/ui/events/event_switches.cc
index 93e938ffe7a4ea911e067b944c28eea67da9c9f7..d5109700a9d5714f402ed22bfc06947fe8b0c829 100644
--- a/ui/events/event_switches.cc
+++ b/ui/events/event_switches.cc
@@ -19,8 +19,18 @@ const char kTouchEventsAuto[] = "auto";
 const char kTouchEventsEnabled[] = "enabled";
 //   disabled: touch events are disabled.
 const char kTouchEventsDisabled[] = "disabled";
-// Use the unified gesture detector, instead of the aura gesture detector.
-const char kUseUnifiedGestureDetector[] = "use-unified-gesture-detector";
+
+// Enable the unified gesture detector, instead of the aura gesture detector.
+const char kUnifiedGestureDetector[] = "unified-gesture-detector";
+
+// The values the kUnifiedGestureDetector switch may have, as in
+// --unified-gesture-detector=disabled.
+//   auto: Same as disabled.
+const char kUnifiedGestureDetectorAuto[] = "auto";
+//   enabled: Use the unified gesture detector.
+const char kUnifiedGestureDetectorEnabled[] = "enabled";
+//   disabled: Use the aura gesture detector.
+const char kUnifiedGestureDetectorDisabled[] = "disabled";
 
 #if defined(OS_LINUX)
 // Tells chrome to interpret events from these devices as touch events. Only