Events ignoring ack disposition receive synthetic acks.

content/common/input/web_input_event_traits.cc

Index: content/common/input/web_input_event_traits.cc
diff --git a/content/common/input/web_input_event_traits.cc b/content/common/input/web_input_event_traits.cc
index 2f2eb7f098fe67e217d0e3a16159c56bb9f8722e..56894ec5442b80d0d2a1966cdcba42dffa73dd2f 100644
--- a/content/common/input/web_input_event_traits.cc
+++ b/content/common/input/web_input_event_traits.cc
@@ -283,4 +283,12 @@ void WebInputEventTraits::Coalesce(const WebInputEvent& event_to_coalesce,
   Apply(WebInputEventCoalesce(), event->type, event_to_coalesce, event);
 }
 
+bool WebInputEventTraits::IgnoresAckDisposition(
+    WebKit::WebInputEvent::Type type) {
+  return type == WebInputEvent::GestureTapDown ||
+      type == WebInputEvent::GestureShowPress ||
+      type == WebInputEvent::GestureTapCancel ||

[jdduke (slow), 2013/10/25 21:00:38]

If adding GestureTap + GestureTapCancel are giving you trouble, you might just
stick with GestureTapDown + GestureShowPress and treat this patch as a
refactoring, adding the other gesture types in a followup patch.

[tdresser, 2013/11/04 15:57:30]

Done.

+      type == WebInputEvent::GestureTap;
+}
+
 }  // namespace content