Coalesce async touch move events until the ack back from render

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 6ca962b5720d9741d2b6bc4d4d251f7e9a86b9ec..10a28c18dbf0caf699c98e46f0575f964ddaacec 100644
--- a/content/common/input/web_input_event_traits.cc
+++ b/content/common/input/web_input_event_traits.cc
@@ -9,6 +9,7 @@
 
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
+#include "content/common/input_messages.h"
 
 using base::StringAppendF;
 using base::SStringPrintf;
@@ -461,7 +462,8 @@ void WebInputEventTraits::Coalesce(const WebInputEvent& event_to_coalesce,
   Apply(WebInputEventCoalesce(), event->type, event_to_coalesce, event);
 }
 
-bool WebInputEventTraits::IgnoresAckDisposition(const WebInputEvent& event) {
+bool WebInputEventTraits::WillReceiveAckFromRenderer(
+    const WebInputEvent& event) {
   switch (event.type) {
     case WebInputEvent::MouseDown:
     case WebInputEvent::MouseUp:
@@ -477,14 +479,43 @@ bool WebInputEventTraits::IgnoresAckDisposition(const WebInputEvent& event) {
     case WebInputEvent::GesturePinchBegin:
     case WebInputEvent::GesturePinchEnd:
     case WebInputEvent::TouchCancel:
-      return true;
+      return false;
     case WebInputEvent::TouchStart:
-    case WebInputEvent::TouchMove:
     case WebInputEvent::TouchEnd:
-      return !static_cast<const WebTouchEvent&>(event).cancelable;
+      return static_cast<const WebTouchEvent&>(event).cancelable;
     default:
-      return false;
+      return true;
+  }
+}
+
+scoped_ptr<IPC::Message> WebInputEventTraits::CreateAckIfNecessary(
+    const blink::WebInputEvent& event,
+    const content::InputEventAckState ack_state,
+    const ui::LatencyInfo& latency_info,
+    scoped_ptr<DidOverscrollParams> overscroll_params,
+    int routing_id) {
+  scoped_ptr<IPC::Message> response;
+  if (event.type == WebInputEvent::TouchMove) {
+    const WebTouchEvent& touch = static_cast<const WebTouchEvent&>(event);
+    if (!touch.cancelable) {
+      response = scoped_ptr<IPC::Message>(

[jdduke (slow), 2015/04/15 17:14:53]

I think we can just do:

return make_scoped_ptr(new ...);

[lanwei, 2015/04/17 20:49:00]

Done.

+          new InputHostMsg_HandleUncancelableTouchMoveEvent_ACK(routing_id));
+      return response.Pass();
+    }
+  }
+
+  const bool send_ack = WebInputEventTraits::WillReceiveAckFromRenderer(event);
+  if (send_ack) {
+    DCHECK(!response);
+    InputHostMsg_HandleInputEvent_ACK_Params ack;
+    ack.type = event.type;
+    ack.state = ack_state;
+    ack.latency = latency_info;
+    ack.overscroll = overscroll_params.Pass();
+    response = scoped_ptr<IPC::Message>(

[jdduke (slow), 2015/04/15 17:14:53]

Same here, |return make_scoped_ptr(new ...)|.

[lanwei, 2015/04/17 20:49:00]

Done.

+        new InputHostMsg_HandleInputEvent_ACK(routing_id, ack));
   }
+  return response.Pass();

[jdduke (slow), 2015/04/15 17:14:53]

Then this just becomes |return nullptr;|

[lanwei, 2015/04/17 20:49:00]

Done.

 }
 
 }  // namespace content