Changes MouseEvent constructor to take changed_button_flags.

ui/events/event.cc

Index: ui/events/event.cc
diff --git a/ui/events/event.cc b/ui/events/event.cc
index 246e39721f2f6a20ec8c75c339ea95721c1f3a6a..22e1625add8b3219ee53f93f21ec9fc9d6b6fc6e 100644
--- a/ui/events/event.cc
+++ b/ui/events/event.cc
@@ -281,9 +281,10 @@ MouseEvent::MouseEvent(const base::NativeEvent& native_event)
 MouseEvent::MouseEvent(EventType type,
                        const gfx::Point& location,
                        const gfx::Point& root_location,
-                       int flags)
+                       int flags,
+                       int changed_button_flags)
     : LocatedEvent(type, location, root_location, EventTimeForNow(), flags),
-      changed_button_flags_(0) {
+      changed_button_flags_(changed_button_flags) {
   if (this->type() == ET_MOUSE_MOVED && IsAnyButton())
     SetType(ET_MOUSE_DRAGGED);
 }
@@ -664,7 +665,7 @@ ScrollEvent::ScrollEvent(EventType type,
                          float x_offset_ordinal,
                          float y_offset_ordinal,
                          int finger_count)
-    : MouseEvent(type, location, location, flags),
+    : MouseEvent(type, location, location, flags, 0),
       x_offset_(x_offset),
       y_offset_(y_offset),
       x_offset_ordinal_(x_offset_ordinal),