Coalesce async touch move events until the ack back from render

content/browser/renderer_host/input/input_router_impl.cc

Index: content/browser/renderer_host/input/input_router_impl.cc
diff --git a/content/browser/renderer_host/input/input_router_impl.cc b/content/browser/renderer_host/input/input_router_impl.cc
index d6fcb1c4f8be948d350401fd1e234e4bea707931..e5ca61612f75eb3f1a044bbcbbcb0f23713724f6 100644
--- a/content/browser/renderer_host/input/input_router_impl.cc
+++ b/content/browser/renderer_host/input/input_router_impl.cc
@@ -257,6 +257,8 @@ bool InputRouterImpl::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(InputRouterImpl, message)
     IPC_MESSAGE_HANDLER(InputHostMsg_HandleInputEvent_ACK, OnInputEventAck)
+    IPC_MESSAGE_HANDLER(InputHostMsg_HandleUncancelableTouchMoveEvent_ACK,
+                        OnUncancelableTouchMoveAck)
     IPC_MESSAGE_HANDLER(InputHostMsg_DidOverscroll, OnDidOverscroll)
     IPC_MESSAGE_HANDLER(InputHostMsg_MoveCaret_ACK, OnMsgMoveCaretAck)
     IPC_MESSAGE_HANDLER(InputHostMsg_SelectRange_ACK, OnSelectMessageAck)
@@ -356,10 +358,12 @@ void InputRouterImpl::OfferToHandlers(const WebInputEvent& input_event,
 
   // Touch events should always indicate in the event whether they are
   // cancelable (respect ACK disposition) or not.
-  bool ignores_ack = WebInputEventTraits::IgnoresAckDisposition(input_event);
-  if (WebInputEvent::isTouchEventType(input_event.type)) {
+  bool ignores_ack =

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

Let's change this to read:

|bool needs_synthetic_ack =
WebInputEventTraits::WillReceiveAckFromRenderer(input_event);|

Might be worth adding a brief router test to make sure we get balanced ack
counts for both a cancelable and uncancelable touchmove?

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

Done.

+      !WebInputEventTraits::WillReceiveAckFromRenderer(input_event);
+  if (WebInputEvent::isTouchEventType(input_event.type) &&
+      input_event.type != WebInputEvent::TouchMove) {
     const WebTouchEvent& touch = static_cast<const WebTouchEvent&>(input_event);
-    DCHECK_NE(ignores_ack, !!touch.cancelable);
+    DCHECK_NE(ignores_ack, touch.cancelable);
   }
 
   // If we don't care about the ack disposition, send the ack immediately.
@@ -405,7 +409,7 @@ bool InputRouterImpl::OfferToRenderer(const WebInputEvent& input_event,
     // Ack messages for ignored ack event types should never be sent by the
     // renderer. Consequently, such event types should not affect event time
     // or in-flight event count metrics.
-    if (!WebInputEventTraits::IgnoresAckDisposition(input_event)) {
+    if (WebInputEventTraits::WillReceiveAckFromRenderer(input_event)) {
       input_event_start_time_ = TimeTicks::Now();
       client_->IncrementInFlightEventCount();
     }
@@ -445,6 +449,10 @@ void InputRouterImpl::OnInputEventAck(
       Details<int>(&type));
 }
 
+void InputRouterImpl::OnUncancelableTouchMoveAck() {
+  touch_event_queue_.ProcessUncancelableTouchMoveAck();

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

We also need:

client_->DecrementInFlightEventCount();
UMA_HISTOGRAM_TIMES("MPArch.IIR_InputEventDelta", TimeTicks::Now() -
input_event_start_time_);

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

Done.

+}
+
 void InputRouterImpl::OnDidOverscroll(const DidOverscrollParams& params) {
   client_->DidOverscroll(params);
 }