Coalesce async touch move events until the ack back from render

content/common/input/input_event_ack.cc

Index: content/common/input/input_event_ack.cc
diff --git a/content/common/input/input_event_ack.cc b/content/common/input/input_event_ack.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3cf86b0da0f77e0de9403f2deade49c2fbd40efa
--- /dev/null
+++ b/content/common/input/input_event_ack.cc
@@ -0,0 +1,41 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/common/input/input_event_ack.h"
+
+namespace content {
+
+InputEventAck::InputEventAck(
+    blink::WebInputEvent::Type type,
+    InputEventAckState state,
+    const ui::LatencyInfo& latency,
+    scoped_ptr<content::DidOverscrollParams> overscroll,
+    uint32 unique_touch_event_id)
+    : type(type),
+      state(state),
+      latency(latency),
+      overscroll(overscroll.Pass()),
+      unique_touch_event_id(unique_touch_event_id) {
+}
+
+InputEventAck::InputEventAck(blink::WebInputEvent::Type type,
+                             InputEventAckState state,
+                             const ui::LatencyInfo& latency,
+                             uint32 unique_touch_event_id)
+    : InputEventAck(type, state, latency, nullptr, unique_touch_event_id) {
+}
+
+InputEventAck::InputEventAck(blink::WebInputEvent::Type type,
+                             InputEventAckState state)
+    : InputEventAck(type, state, ui::LatencyInfo(), 0) {
+}
+
+InputEventAck::InputEventAck()
+     : unique_touch_event_id(0) {

[jdduke (slow), 2015/05/08 21:30:49]

We should also initialize type (to WebInputEvent::Unknown) and state (to
INPUT_EVENT_ACK_STATE_UNKNOWN).

[lanwei, 2015/05/11 19:27:56]

Done.

+}
+
+InputEventAck::~InputEventAck() {
+}
+
+}  // namespace content