Revert "Ensure that TouchEvents are always async after scrolling has started."

This reverts commit f4886cba.

Reason for revert: This causes unintended throttling of TouchMoves if
the page is at the overflow already. Fix will land in next release.
See crbug/1123304 for details.


Original change's description:
> Ensure that TouchEvents are always async after scrolling has started.
>
> Currently we can flip flop back and forth between TouchMoves being sent
> async or sync which can cause some pretty noticeable cases of jank. This
> ensures that we are always consistently scrolling after deciding
> TouchMoves can be async.
>
> Bug: 1072364
> Change-Id: I3ef1ed6715d4b1fd2d3e1377ebd6b0c8bcc02872
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2182426
> Commit-Queue: Stephen Nusko <nuskos@chromium.org>
> Auto-Submit: Stephen Nusko <nuskos@chromium.org>
> Reviewed-by: David Bokan <bokan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#776487}

TBR=bokan@chromium.org,nuskos@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1072364,1123304
Change-Id: I7645aa130ddaf5214bde77a8cbcdd239e48f729c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2413491
Auto-Submit: Stephen Nusko <nuskos@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Reviewed-by: Stephen Nusko <nuskos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807464}

content/browser/renderer_host/input/input_router_impl_unittest.cc

@@ -1676,9 +1676,6 @@ TEST_F(InputRouterImplTest, AsyncTouchMoveAckedImmediately) {
   dispatched_messages[0]->ToEvent()->CallCallback(
       blink::mojom::InputEventResultState::kConsumed);
   EXPECT_EQ(1U, disposition_handler_->GetAndResetAckCount());
-  EXPECT_EQ(WebInputEvent::Type::kTouchStart,
-            disposition_handler_->ack_event_type());
-
   SimulateGestureEvent(WebInputEvent::Type::kGestureScrollBegin,
                        blink::WebGestureDevice::kTouchscreen);
   dispatched_messages = GetAndResetDispatchedMessages();
@@ -1687,55 +1684,14 @@ TEST_F(InputRouterImplTest, AsyncTouchMoveAckedImmediately) {
   dispatched_messages[0]->ToEvent()->CallCallback(
       blink::mojom::InputEventResultState::kConsumed);
   EXPECT_EQ(1U, disposition_handler_->GetAndResetAckCount());
-  EXPECT_EQ(WebInputEvent::Type::kGestureScrollBegin,
-            disposition_handler_->ack_event_type());
-
   SimulateGestureEvent(WebInputEvent::Type::kGestureScrollUpdate,
                        blink::WebGestureDevice::kTouchscreen);
   EXPECT_EQ(0U, disposition_handler_->GetAndResetAckCount());
-  dispatched_messages = GetAndResetDispatchedMessages();
-  EXPECT_EQ(2U, dispatched_messages.size());
-  EXPECT_EQ(WebInputEvent::Type::kTouchScrollStarted,
-            dispatched_messages[0]->ToEvent()->Event()->Event().GetType());
-  EXPECT_EQ(WebInputEvent::Type::kGestureScrollUpdate,
-            dispatched_messages[1]->ToEvent()->Event()->Event().GetType());
-  // Ack the GestureScrollUpdate.
-  dispatched_messages[1]->ToEvent()->CallCallback(
-      blink::mojom::InputEventResultState::kConsumed);
-  EXPECT_EQ(WebInputEvent::Type::kGestureScrollUpdate,
-            disposition_handler_->ack_event_type());
-  EXPECT_EQ(1U, disposition_handler_->GetAndResetAckCount());
+  EXPECT_EQ(2U, GetAndResetDispatchedMessages().size());
 
-  // Now since we're scrolling send an async move.
+  // Now send an async move.
   MoveTouchPoint(0, 5, 5);
   SendTouchEvent();
-  EXPECT_EQ(WebInputEvent::Type::kTouchMove,
-            disposition_handler_->ack_event_type());
-  EXPECT_EQ(1U, disposition_handler_->GetAndResetAckCount());
-  EXPECT_EQ(1U, GetAndResetDispatchedMessages().size());
-
-  // To catch crbug/1072364 send another scroll which returns kNoConsumerExists
-  // and ensure we're still async scrolling since we've already started the
-  // scroll.
-  SimulateGestureEvent(WebInputEvent::Type::kGestureScrollUpdate,
-                       blink::WebGestureDevice::kTouchscreen);
-  EXPECT_EQ(0U, disposition_handler_->GetAndResetAckCount());
-  dispatched_messages = GetAndResetDispatchedMessages();
-  EXPECT_EQ(1U, dispatched_messages.size());
-  EXPECT_EQ(WebInputEvent::Type::kGestureScrollUpdate,
-            dispatched_messages[0]->ToEvent()->Event()->Event().GetType());
-  // Ack the GestureScrollUpdate.
-  dispatched_messages[0]->ToEvent()->CallCallback(
-      blink::mojom::InputEventResultState::kNoConsumerExists);
-  EXPECT_EQ(WebInputEvent::Type::kGestureScrollUpdate,
-            disposition_handler_->ack_event_type());
-  EXPECT_EQ(1U, disposition_handler_->GetAndResetAckCount());
-
-  // Now since we're scrolling (even with NoConsumerExists) send an async move.
-  MoveTouchPoint(0, 10, 5);
-  SendTouchEvent();
-  EXPECT_EQ(WebInputEvent::Type::kTouchMove,
-            disposition_handler_->ack_event_type());
   EXPECT_EQ(1U, disposition_handler_->GetAndResetAckCount());
   EXPECT_EQ(1U, GetAndResetDispatchedMessages().size());
 }

content/browser/renderer_host/input/passthrough_touch_event_queue.cc

@@ -145,7 +145,6 @@ void PassthroughTouchEventQueue::ProcessTouchAck(
 
 void PassthroughTouchEventQueue::OnGestureScrollEvent(
     const GestureEventWithLatencyInfo& gesture_event) {
-  // Turn events sent during gesture scrolls to be async.
   if (gesture_event.event.GetType() ==
       blink::WebInputEvent::Type::kGestureScrollUpdate) {
     send_touch_events_async_ = true;
@@ -155,12 +154,11 @@ void PassthroughTouchEventQueue::OnGestureScrollEvent(
 void PassthroughTouchEventQueue::OnGestureEventAck(
     const GestureEventWithLatencyInfo& event,
     blink::mojom::InputEventResultState ack_result) {
-  // When the scroll finishes allow TouchEvents to be blocking again.
-  if (event.event.GetType() == blink::WebInputEvent::Type::kGestureScrollEnd) {
-    send_touch_events_async_ = false;
-  } else if (event.event.GetType() ==
-             blink::WebInputEvent::Type::kGestureScrollUpdate) {
-    send_touch_events_async_ = true;
+  // Turn events sent during gesture scrolls to be async.
+  if (event.event.GetType() ==
+      blink::WebInputEvent::Type::kGestureScrollUpdate) {
+    send_touch_events_async_ =
+        (ack_result == blink::mojom::InputEventResultState::kConsumed);
   }
 }