Turn MoveLeave event sending into a feature for testing enabling it.

ui/events/blink/web_input_event.cc

Index: ui/events/blink/web_input_event.cc
diff --git a/ui/events/blink/web_input_event.cc b/ui/events/blink/web_input_event.cc
index 10b13b57c8bbee1c9994721b49a74e8a4aeb1a01..3476f003322d260072713e558e7fabcc0b744721 100644
--- a/ui/events/blink/web_input_event.cc
+++ b/ui/events/blink/web_input_event.cc
@@ -6,6 +6,7 @@
 
 #include "ui/events/base_event_utils.h"
 #include "ui/events/blink/blink_event_util.h"
+#include "ui/events/blink/blink_features.h"
 #include "ui/events/event.h"
 #include "ui/events/event_utils.h"
 #include "ui/events/keycodes/dom/keycode_converter.h"
@@ -385,13 +386,13 @@ blink::WebMouseEvent MakeWebMouseEventFromUiEvent(const MouseEvent& event) {
       type = blink::WebInputEvent::MouseUp;
       click_count = event.GetClickCount();
       break;
-    case ET_MOUSE_EXITED:
-// TODO(chaopeng) this fix only for chromeos now, should convert ET_MOUSE_EXITED
-// to MouseLeave when crbug.com/450631 fixed.
-#if defined(OS_CHROMEOS)
-      type = blink::WebInputEvent::MouseLeave;
+    case ET_MOUSE_EXITED: {
+      static bool s_send_leave =
+          base::FeatureList::IsEnabled(features::kSendMouseLeaveEvents);
+      type = s_send_leave ? blink::WebInputEvent::MouseLeave
+                          : blink::WebInputEvent::MouseMove;
       break;
-#endif
+    }
     case ET_MOUSE_ENTERED:
     case ET_MOUSE_MOVED:
     case ET_MOUSE_DRAGGED: