Fixes bug where Env/RootWindow would cache the wrong button

ui/base/win/events_win.cc

Index: ui/base/win/events_win.cc
diff --git a/ui/base/win/events_win.cc b/ui/base/win/events_win.cc
index 212002597b22b0f23bdff88b2e93df532f84414a..3ea2f75eca868190bd6e1da3b3a7c16626292e8d 100644
--- a/ui/base/win/events_win.cc
+++ b/ui/base/win/events_win.cc
@@ -224,6 +224,12 @@ bool IsMouseEvent(const base::NativeEvent& native_event) {
          IsNonClientMouseEvent(native_event);
 }
 
+int GetChangedMouseButtonFlagsFromNative(
+    const base::NativeEvent& native_event) {
+  // TODO(sky): implement me.
+  return 0;
+}
+
 int GetMouseWheelOffset(const base::NativeEvent& native_event) {
   DCHECK(native_event.message == WM_MOUSEWHEEL);
   return GET_WHEEL_DELTA_WPARAM(native_event.wParam);