Notify Blink about start of gesture scroll through a queued event.

content/browser/renderer_host/input/input_router_impl_unittest.cc

Index: content/browser/renderer_host/input/input_router_impl_unittest.cc
diff --git a/content/browser/renderer_host/input/input_router_impl_unittest.cc b/content/browser/renderer_host/input/input_router_impl_unittest.cc
index 861ecaeefa8004ed06933875779aff2598ec5a36..aa91bd951c7d78a88feeebce4ea04c7564b2208e 100644
--- a/content/browser/renderer_host/input/input_router_impl_unittest.cc
+++ b/content/browser/renderer_host/input/input_router_impl_unittest.cc
@@ -274,6 +274,12 @@ class InputRouterImplTest : public testing::Test {
     return touch_event_id;
   }
 
+  void ProcessSyntheticInputEventAck(WebInputEvent::Type type) {

[tdresser, 2016/04/01 14:50:24]

Let's make this method more specific - something like
AckTouchScrollStartedNotification, and add a comment on why it's needed.

[mustaq, 2016/04/01 18:31:04]

Done.

+    ui::LatencyInfo latency_info;
+    input_router_->ProcessInputEventAck(type, INPUT_EVENT_ACK_STATE_IGNORED,
+        latency_info, 0, InputRouterImpl::IGNORING_DISPOSITION);
+  }
+
   int PressTouchPoint(int x, int y) {
     return touch_event_.PressPoint(x, y);
   }
@@ -1103,6 +1109,9 @@ TEST_F(InputRouterImplTest, GestureTypesIgnoringAck) {
     EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
     EXPECT_EQ(1U, ack_handler_->GetAndResetAckCount());
     EXPECT_EQ(0, client_->in_flight_event_count());
+
+    if (type == WebInputEvent::GestureScrollBegin)
+      ProcessSyntheticInputEventAck(WebInputEvent::TouchScrollStarted);
     EXPECT_FALSE(HasPendingEvents());
   }
 }
@@ -1233,7 +1242,6 @@ TEST_F(InputRouterImplTest, GestureShowPressIsInOrder) {
   EXPECT_EQ(1U, GetSentMessageCountAndResetSink());
   EXPECT_EQ(1U, ack_handler_->GetAndResetAckCount());
 
-
   // GesturePinchBegin ignores its ack.
   SimulateGestureEvent(WebInputEvent::GesturePinchBegin,
                        blink::WebGestureDeviceTouchscreen);
@@ -1692,6 +1700,7 @@ TEST_F(InputRouterImplTest, InputFlushAfterFling) {
                        blink::WebGestureDeviceTouchscreen);
   SimulateGestureEvent(WebInputEvent::GestureFlingStart,
                        blink::WebGestureDeviceTouchscreen);
+  ProcessSyntheticInputEventAck(WebInputEvent::TouchScrollStarted);

[tdresser, 2016/04/01 14:50:24]

Shouldn't we assert somewhere that we output TouchScrollStarted events?

[mustaq, 2016/04/01 18:31:04]

The existing tests here only care about events passed upstream of
input_event_router, between RH & the router. The TouchScrollStarted event is
strictly downstream, and I have the check already in TouchEventQueueTest.

Testing TouchScrollStarted here would require pulling TouchEventQueueTest logic
into this file, which violates the "unittest" concept.

I added queue size checks below wherever we have only the new event in the
queue.

   EXPECT_TRUE(HasPendingEvents());
 
   // If the fling is unconsumed, the flush is complete.
@@ -1701,7 +1710,9 @@ TEST_F(InputRouterImplTest, InputFlushAfterFling) {
                        blink::WebGestureDeviceTouchscreen);
   SendInputEventACK(WebInputEvent::GestureFlingStart,
                     INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  ProcessSyntheticInputEventAck(WebInputEvent::TouchScrollStarted);
   EXPECT_FALSE(HasPendingEvents());
+
   EXPECT_EQ(1U, GetAndResetDidFlushCount());
 
   // Simulate a second fling.
@@ -1728,6 +1739,7 @@ TEST_F(InputRouterImplTest, InputFlushAfterFling) {
                        blink::WebGestureDeviceTouchscreen);
   SimulateGestureEvent(WebInputEvent::GestureFlingStart,
                        blink::WebGestureDeviceTouchscreen);
+  ProcessSyntheticInputEventAck(WebInputEvent::TouchScrollStarted);
   ASSERT_TRUE(HasPendingEvents());
   RequestNotificationWhenFlushed();
   EXPECT_EQ(0U, GetAndResetDidFlushCount());