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

ui/events/blink/blink_event_util.cc

Index: ui/events/blink/blink_event_util.cc
diff --git a/ui/events/blink/blink_event_util.cc b/ui/events/blink/blink_event_util.cc
index 6378ce21ff9968ecc7e1652a547c9d451f982fbf..ac5a14aa438e64447b6d164dd6e5e71aa0ce581e 100644
--- a/ui/events/blink/blink_event_util.cc
+++ b/ui/events/blink/blink_event_util.cc
@@ -670,11 +670,17 @@ WebGestureEvent CreateWebGestureEvent(const GestureEventDetails& details,
       gesture.data.scrollBegin.pointerCount = details.touch_points();
       gesture.data.scrollBegin.deltaXHint = details.scroll_x_hint();
       gesture.data.scrollBegin.deltaYHint = details.scroll_y_hint();
+      gesture.data.scrollBegin.deltaHintUnits =
+          static_cast<blink::WebGestureEvent::ScrollUnits>(
+              details.scroll_begin_units());
       break;
     case ET_GESTURE_SCROLL_UPDATE:
       gesture.setType(WebInputEvent::GestureScrollUpdate);
       gesture.data.scrollUpdate.deltaX = details.scroll_x();
       gesture.data.scrollUpdate.deltaY = details.scroll_y();
+      gesture.data.scrollUpdate.deltaUnits =
+          static_cast<blink::WebGestureEvent::ScrollUnits>(
+              details.scroll_update_units());
       gesture.data.scrollUpdate.previousUpdateInSequencePrevented =
           details.previous_scroll_update_in_sequence_prevented();
       break;
@@ -750,10 +756,12 @@ std::unique_ptr<blink::WebInputEvent> TranslateAndScaleWebInputEvent(
     wheel_event->y += delta.y();
     wheel_event->x *= scale;
     wheel_event->y *= scale;
-    wheel_event->deltaX *= scale;
-    wheel_event->deltaY *= scale;
-    wheel_event->wheelTicksX *= scale;
-    wheel_event->wheelTicksY *= scale;
+    if (!wheel_event->scrollByPage) {

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

Test for this too?

[chengx, 2017/02/17 21:57:44]

Yep, added.

+      wheel_event->deltaX *= scale;
+      wheel_event->deltaY *= scale;
+      wheel_event->wheelTicksX *= scale;
+      wheel_event->wheelTicksY *= scale;
+    }
   } else if (blink::WebInputEvent::isMouseEventType(event.type())) {
     blink::WebMouseEvent* mouse_event = new blink::WebMouseEvent;
     scaled_event.reset(mouse_event);
@@ -788,12 +796,18 @@ std::unique_ptr<blink::WebInputEvent> TranslateAndScaleWebInputEvent(
     gesture_event->y *= scale;
     switch (gesture_event->type()) {
       case blink::WebInputEvent::GestureScrollUpdate:
-        gesture_event->data.scrollUpdate.deltaX *= scale;
-        gesture_event->data.scrollUpdate.deltaY *= scale;
+        if (gesture_event->data.scrollUpdate.deltaUnits !=
+            blink::WebGestureEvent::ScrollUnits::Page) {
+          gesture_event->data.scrollUpdate.deltaX *= scale;
+          gesture_event->data.scrollUpdate.deltaY *= scale;
+        }
         break;
       case blink::WebInputEvent::GestureScrollBegin:
-        gesture_event->data.scrollBegin.deltaXHint *= scale;
-        gesture_event->data.scrollBegin.deltaYHint *= scale;
+        if (gesture_event->data.scrollBegin.deltaHintUnits !=
+            blink::WebGestureEvent::ScrollUnits::Page) {
+          gesture_event->data.scrollBegin.deltaXHint *= scale;
+          gesture_event->data.scrollBegin.deltaYHint *= scale;
+        }
         break;
 
       case blink::WebInputEvent::GesturePinchUpdate: