Fix mouse wheel over-scrolls when display is scaled and scroll is paginated

ui/events/blink/blink_event_util_unittest.cc

Index: ui/events/blink/blink_event_util_unittest.cc
diff --git a/ui/events/blink/blink_event_util_unittest.cc b/ui/events/blink/blink_event_util_unittest.cc
index 1bee59157f5832fa87e92ad83c5ee0bbe761ba49..eb82995c5fcb1b55bf7a4587af65b68924056a44 100644
--- a/ui/events/blink/blink_event_util_unittest.cc
+++ b/ui/events/blink/blink_event_util_unittest.cc
@@ -28,6 +28,36 @@ TEST(BlinkEventUtilTest, NoScalingWith1DSF) {
   EXPECT_TRUE(ScaleWebInputEvent(event, 2.f));
 }
 
+TEST(BlinkEventUtilTest, PaginatedScrollBeginEvent) {
+  ui::GestureEventDetails details(ui::ET_GESTURE_SCROLL_BEGIN, 1, 1,
+                                  ui::GestureEventDetails::ScrollUnits::PAGE);
+  details.set_device_type(ui::GestureDeviceType::DEVICE_TOUCHSCREEN);
+  auto event =
+      CreateWebGestureEvent(details, base::TimeTicks(), gfx::PointF(1.f, 1.f),
+                            gfx::PointF(1.f, 1.f), 0, 0U);
+  std::unique_ptr<blink::WebInputEvent> webEvent =
+      ScaleWebInputEvent(event, 2.f);
+  EXPECT_TRUE(webEvent);
+  blink::WebGestureEvent* gestureEvent =
+      static_cast<blink::WebGestureEvent*>(webEvent.get());
+  EXPECT_EQ(1, gestureEvent->data.scrollUpdate.deltaY);

[Bret, 2017/02/17 21:06:03]

nit: it's probably worth adding the one line to check deltaX too (and below).

[chengx, 2017/02/17 21:57:45]

Added checks for deltaX. Also, I should use scrollBegin* here. It is fixed now.

+}
+
+TEST(BlinkEventUtilTest, PaginatedScrollUpdateEvent) {
+  ui::GestureEventDetails details(ui::ET_GESTURE_SCROLL_UPDATE, 1, 1,
+                                  ui::GestureEventDetails::ScrollUnits::PAGE);
+  details.set_device_type(ui::GestureDeviceType::DEVICE_TOUCHSCREEN);
+  auto event =
+      CreateWebGestureEvent(details, base::TimeTicks(), gfx::PointF(1.f, 1.f),
+                            gfx::PointF(1.f, 1.f), 0, 0U);
+  std::unique_ptr<blink::WebInputEvent> webEvent =
+      ScaleWebInputEvent(event, 2.f);
+  EXPECT_TRUE(webEvent);
+  blink::WebGestureEvent* gestureEvent =
+      static_cast<blink::WebGestureEvent*>(webEvent.get());
+  EXPECT_EQ(1, gestureEvent->data.scrollUpdate.deltaY);
+}
+
 TEST(BlinkEventUtilTest, TouchEventCoalescing) {
   blink::WebTouchPoint touch_point;
   touch_point.id = 1;