Touch Action could cause wheel gestures to be filtered.

content/browser/renderer_host/input/input_router_impl_unittest.cc

 // Copyright 2013 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 <math.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/command_line.h"
 #include "base/location.h"
@@ skipping 2198 matching lines @@
   EXPECT_EQ(20.f, sent_event->data.scrollUpdate.deltaX);
   EXPECT_EQ(40.f, sent_event->data.scrollUpdate.deltaY);
 
   const WebGestureEvent* filter_event =
       GetFilterWebInputEvent<WebGestureEvent>();
   EXPECT_EQ(10.f, filter_event->data.scrollUpdate.deltaX);
   EXPECT_EQ(20.f, filter_event->data.scrollUpdate.deltaY);
 }
 
 TEST_F(InputRouterImplScaleGestureEventTest, GestureScrollBegin) {
-  SimulateGestureEvent(
-      SyntheticWebGestureEventBuilder::BuildScrollBegin(10.f, 20.f));
+  SimulateGestureEvent(SyntheticWebGestureEventBuilder::BuildScrollBegin(
+      10.f, 20.f, blink::WebGestureDeviceTouchscreen));
   const WebGestureEvent* sent_event = GetSentWebInputEvent<WebGestureEvent>();
   EXPECT_EQ(20.f, sent_event->data.scrollBegin.deltaXHint);
   EXPECT_EQ(40.f, sent_event->data.scrollBegin.deltaYHint);
 
   const WebGestureEvent* filter_event =
       GetFilterWebInputEvent<WebGestureEvent>();
   EXPECT_EQ(10.f, filter_event->data.scrollBegin.deltaXHint);
   EXPECT_EQ(20.f, filter_event->data.scrollBegin.deltaYHint);
 }
 
@@ skipping 98 matching lines @@
   EXPECT_EQ(80, sent_event->data.flingStart.velocityY);
 
   const WebGestureEvent* filter_event =
       GetFilterWebInputEvent<WebGestureEvent>();
   TestLocationInFilterEvent(filter_event, orig);
   EXPECT_EQ(30, filter_event->data.flingStart.velocityX);
   EXPECT_EQ(40, filter_event->data.flingStart.velocityY);
 }
 
 }  // namespace content