Make first TouchStart and first TouchMove events on a flinging layer non-blocking

content/renderer/input/main_thread_event_queue.cc

Index: content/renderer/input/main_thread_event_queue.cc
diff --git a/content/renderer/input/main_thread_event_queue.cc b/content/renderer/input/main_thread_event_queue.cc
index 772d3be1c6bc31a979561586ac353b966ba1780a..5fe5bff6786ccd2049a3735d2c9cca77ccac7d09 100644
--- a/content/renderer/input/main_thread_event_queue.cc
+++ b/content/renderer/input/main_thread_event_queue.cc
@@ -41,7 +41,8 @@ MainThreadEventQueue::MainThreadEventQueue(
     : routing_id_(routing_id),
       client_(client),
       is_flinging_(false),
-      main_task_runner_(main_task_runner) {}
+      main_task_runner_(main_task_runner),
+      waiting_for_first_touch_move_(false) {}
 
 MainThreadEventQueue::~MainThreadEventQueue() {}
 
@@ -77,6 +78,21 @@ bool MainThreadEventQueue::HandleEvent(
       touch_event.dispatchType =
           blink::WebInputEvent::ListenersNonBlockingPassive;
     }
+    if (is_flinging_ &&

[dtapuska, 2016/08/10 14:47:42]

does |is_flinging_| change after the touch start?

I'm not sure what buying the first touch move after touch start is buying us
here; as opposed to  checking if the event is cancelable which you are checking
if it is blocking.

Perhaps we should add is first touch move after start just to the web input
event and avoid all these states all over the place?

+        touch_event.dispatchType == blink::WebInputEvent::Blocking) {
+      bool touch_start_or_first_touch_move = false;
+      if (event->type == blink::WebInputEvent::TouchStart) {
+        waiting_for_first_touch_move_ = true;
+        touch_start_or_first_touch_move = true;
+      } else if (event->type == blink::WebInputEvent::TouchMove) {
+        touch_start_or_first_touch_move = waiting_for_first_touch_move_;
+        waiting_for_first_touch_move_ = false;
+      }
+      if (touch_start_or_first_touch_move) {
+        touch_event.dispatchType =
+            blink::WebInputEvent::ListenersForcedNonBlockingPassiveDueToFling;
+      }
+    }
   }
   if (is_wheel && non_blocking) {
     // Adjust the |dispatchType| on the event since the compositor