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

ui/events/blink/blink_event_util_unittest.cc

 // Copyright 2016 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 "ui/events/blink/blink_event_util.h"
 
 #include "base/time/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/WebKit/public/platform/WebGestureEvent.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
@@ skipping 10 matching lines @@
       CreateWebGestureEvent(details,
                             base::TimeTicks(),
                             gfx::PointF(1.f, 1.f),
                             gfx::PointF(1.f, 1.f),
                             0,
                             0U);
   EXPECT_FALSE(ScaleWebInputEvent(event, 1.f));
   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;
   touch_point.state = blink::WebTouchPoint::StateMoved;
 
   blink::WebTouchEvent coalesced_event;
   coalesced_event.setType(blink::WebInputEvent::TouchMove);
   touch_point.movementX = 5;
   touch_point.movementY = 10;
   coalesced_event.touches[coalesced_event.touchesLength++] = touch_point;
 
   blink::WebTouchEvent event_to_be_coalesced;
   event_to_be_coalesced.setType(blink::WebInputEvent::TouchMove);
   touch_point.movementX = 3;
   touch_point.movementY = -4;
   event_to_be_coalesced.touches[event_to_be_coalesced.touchesLength++] =
       touch_point;
 
   EXPECT_TRUE(CanCoalesce(event_to_be_coalesced, coalesced_event));
   Coalesce(event_to_be_coalesced, &coalesced_event);
   EXPECT_EQ(8, coalesced_event.touches[0].movementX);
   EXPECT_EQ(6, coalesced_event.touches[0].movementY);
 }
 
 }  // namespace ui