Create MouseWheelEvent directly instead of through MouseEvent.

ui/events/event_unittest.cc

Index: ui/events/event_unittest.cc
diff --git a/ui/events/event_unittest.cc b/ui/events/event_unittest.cc
index 83ad2333138fca94303a887dee6f3d203424fbbb..ae9a5d6bd059250861531a725bcfac2a6c220f9e 100644
--- a/ui/events/event_unittest.cc
+++ b/ui/events/event_unittest.cc
@@ -738,14 +738,17 @@ TEST(EventTest, PointerEventCanConvertFrom) {
 
   // Common mouse events can be converted.
   const EventType mouse_allowed[] = {
-      ET_MOUSE_PRESSED, ET_MOUSE_DRAGGED,         ET_MOUSE_MOVED,
-      ET_MOUSE_ENTERED, ET_MOUSE_EXITED,          ET_MOUSE_RELEASED,
-      ET_MOUSEWHEEL,    ET_MOUSE_CAPTURE_CHANGED,
+      ET_MOUSE_PRESSED,         ET_MOUSE_DRAGGED, ET_MOUSE_MOVED,
+      ET_MOUSE_ENTERED,         ET_MOUSE_EXITED,  ET_MOUSE_RELEASED,
+      ET_MOUSE_CAPTURE_CHANGED,
   };
   for (size_t i = 0; i < arraysize(mouse_allowed); i++) {
     MouseEvent event(mouse_allowed[i], point, point, time, 0, 0);
     EXPECT_TRUE(PointerEvent::CanConvertFrom(event));
   }
+  // Mouse wheel events can be converted.
+  MouseWheelEvent event(gfx::Vector2d(), point, point, time, 0, 0);
+  EXPECT_TRUE(PointerEvent::CanConvertFrom(event));
 
   // Common touch events can be converted.
   const EventType touch_allowed[] = {