[Ozone] Do not warp cursor for synthesized events

This behavior is similar to not having a native event on the non-Ozone path.

Synthesized events were processed after the ScreenPositionClient was removed
from the window. Trying to convert the cursor point to screen coordinates would
trigger a CHECK in ash::wm::ConvertPointToScreen since these synthesized events
would be processed as the WindowTreeHost was shutdown.

BUG=398888
NOTRY=true

Review URL: https://codereview.chromium.org/442033002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287837 0039d316-1c4b-4281-b951-d872f2087c98

ash/display/mouse_cursor_event_filter_ozone.cc

@@ -16,6 +16,9 @@ void MouseCursorEventFilter::OnDisplayConfigurationChanged() {
 }
 
 bool MouseCursorEventFilter::WarpMouseCursorIfNecessary(ui::MouseEvent* event) {
+  if (event->flags() & ui::EF_IS_SYNTHESIZED)
+    return false;
+
   gfx::Point point_in_screen(event->location());
   aura::Window* target = static_cast<aura::Window*>(event->target());
   wm::ConvertPointToScreen(target, &point_in_screen);