Avoid sending touchmove events where all pointers are stationary

content/browser/renderer_host/input/touch_event_queue.cc

Index: content/browser/renderer_host/input/touch_event_queue.cc
diff --git a/content/browser/renderer_host/input/touch_event_queue.cc b/content/browser/renderer_host/input/touch_event_queue.cc
index 6adc661be18c5394f4571ac2d037c11b74133cda..d75fa33eec2e39aa56599a95a918c3292429d588 100644
--- a/content/browser/renderer_host/input/touch_event_queue.cc
+++ b/content/browser/renderer_host/input/touch_event_queue.cc
@@ -46,14 +46,15 @@ bool ShouldTouchTriggerTimeout(const WebTouchEvent& event) {
 }
 
 // Compare all properties of touch points to determine the state.
-bool HasPointChanged(const WebTouchPoint& last_point,
-    const WebTouchPoint& current_point) {
-  if (last_point.screenPosition != current_point.screenPosition ||
-      last_point.position != current_point.position ||
-      last_point.radiusX != current_point.radiusX ||
-      last_point.radiusY != current_point.radiusY ||
-      last_point.rotationAngle != current_point.rotationAngle ||
-      last_point.force != current_point.force) {
+bool HasPointChanged(const WebTouchPoint& point_1,
+    const WebTouchPoint& point_2) {
+  DCHECK_EQ(point_1.id, point_2.id);
+  if (point_1.screenPosition != point_2.screenPosition ||
+      point_1.position != point_2.position ||
+      point_1.radiusX != point_2.radiusX ||
+      point_1.radiusY != point_2.radiusY ||
+      point_1.rotationAngle != point_2.rotationAngle ||
+      point_1.force != point_2.force) {
     return true;
   }
   return false;
@@ -729,12 +730,29 @@ TouchEventQueue::FilterBeforeForwarding(const WebTouchEvent& event) {
         continue;
 
       for (size_t j = 0; j < last_sent_touchevent_->touchesLength; ++j) {
-        if (point.id == last_sent_touchevent_->touches[j].id)
+        if (point.id != last_sent_touchevent_->touches[j].id)
+          continue;
+
+        if (event.type != WebInputEvent::TouchMove)
           return FORWARD_TO_RENDERER;
+
+        // All pointers in TouchMove events may have state as StateMoved,
+        // even though none of the pointers have not changed in real.
+        // Forward these events when at least one pointer has changed.
+        if (HasPointChanged(last_sent_touchevent_->touches[j], point))
+          return FORWARD_TO_RENDERER;
+
+        // This is a TouchMove event and not forwarded yet.

[jdduke (slow), 2015/02/13 16:37:37]

Nit: Maybe reword this like:

// This is a TouchMove event for which we have yet to find a non-stationary
pointer. Continue checking the next pointers in the |event|.

[USE s.singapati at gmail.com, 2015/02/16 10:52:01]

Done.

+        // Continue checking the next pointers in the |event|.
+        break;
       }

[jdduke (slow), 2015/02/13 16:37:37]

It's a shame we can't "clean up" the pointer state here while we're at it, but
that would involve making the argument a pointer and maybe it's not worth it.

[USE s.singapati at gmail.com, 2015/02/16 10:52:01]

Acknowledged. Lets see if this can be done may be after this patch.

+
     }
   }
 
+  if (event.type == WebInputEvent::TouchMove)

[jdduke (slow), 2015/02/13 16:37:37]

This isn't always correct. Let's just go ahead and stick with NO_CONSUMER_EXISTS
for now.

[USE s.singapati at gmail.com, 2015/02/16 10:52:01]

Done.

+    return ACK_WITH_NOT_CONSUMED;
+
   return ACK_WITH_NO_CONSUMER_EXISTS;
 }