Add wheel scroll options "scroll_by_page" to GpuBenchmarking

In GpuBenchmarking, for mouse wheel and touchpad scroll, we want to add
"scroll_by_page" scroll option to GpuBenchmarking::SmoothScrollBy.

Bug: 871970
Change-Id: If73cc2bb41a77499cfc6215b5d8fde09f33f6caa
Reviewed-on: https://chromium-review.googlesource.com/1174993
Commit-Queue: Lan Wei <lanwei@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Sahel Sharify <sahel@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585656}

content/browser/renderer_host/input/synthetic_gesture_controller_unittest.cc

@@ -189,7 +189,9 @@ class MockSyntheticGestureTarget : public SyntheticGestureTarget {
 class MockMoveGestureTarget : public MockSyntheticGestureTarget {
  public:
   MockMoveGestureTarget()
-      : total_abs_move_distance_length_(0), precise_scrolling_deltas_(false) {}
+      : total_abs_move_distance_length_(0),
+        precise_scrolling_deltas_(false),
+        scroll_by_page_(false) {}
   ~MockMoveGestureTarget() override {}
 
   gfx::Vector2dF start_to_end_distance() const {
@@ -199,11 +201,13 @@ class MockMoveGestureTarget : public MockSyntheticGestureTarget {
     return total_abs_move_distance_length_;
   }
   bool precise_scrolling_deltas() const { return precise_scrolling_deltas_; }
+  bool scroll_by_page() const { return scroll_by_page_; }
 
  protected:
   gfx::Vector2dF start_to_end_distance_;
   float total_abs_move_distance_length_;
   bool precise_scrolling_deltas_;
+  bool scroll_by_page_;
 };
 
 class MockScrollMouseTarget : public MockMoveGestureTarget {
@@ -219,6 +223,7 @@ class MockScrollMouseTarget : public MockMoveGestureTarget {
     start_to_end_distance_ += delta;
     total_abs_move_distance_length_ += delta.Length();
     precise_scrolling_deltas_ = mouse_wheel_event.has_precise_scrolling_deltas;
+    scroll_by_page_ = mouse_wheel_event.scroll_by_page;
   }
 };
 
@@ -1258,6 +1263,27 @@ TEST_F(SyntheticGestureControllerTest, SingleScrollGestureMousePreciseScroll) {
             scroll_target->precise_scrolling_deltas());
 }
 
+TEST_F(SyntheticGestureControllerTest, SingleScrollGestureMouseScrollByPage) {
+  CreateControllerAndTarget<MockScrollMouseTarget>();
+
+  SyntheticSmoothMoveGestureParams params;
+  params.input_type = SyntheticSmoothMoveGestureParams::MOUSE_WHEEL_INPUT;
+  params.start_point.SetPoint(39, 86);
+  params.distances.push_back(gfx::Vector2d(0, -132));
+  params.scroll_by_page = true;
+
+  std::unique_ptr<SyntheticSmoothMoveGesture> gesture(
+      new SyntheticSmoothMoveGesture(params));
+  QueueSyntheticGesture(std::move(gesture));
+  FlushInputUntilComplete();
+
+  MockMoveGestureTarget* scroll_target =
+      static_cast<MockMoveGestureTarget*>(target_);
+  EXPECT_EQ(1, num_success_);
+  EXPECT_EQ(0, num_failure_);
+  EXPECT_EQ(params.scroll_by_page, scroll_target->scroll_by_page());
+}
+
 void CheckIsWithinRangeMulti(float scroll_distance,
                              int target_distance,
                              SyntheticGestureTarget* target) {

content/browser/renderer_host/input/synthetic_gesture_target_aura.cc

@@ -81,9 +81,13 @@ void SyntheticGestureTargetAura::DispatchWebMouseWheelEventToPlatform(
     return;
   }
   base::TimeTicks timestamp = web_wheel.TimeStamp();
-  int modifiers = web_wheel.has_precise_scrolling_deltas
-                      ? ui::EF_PRECISION_SCROLLING_DELTA
-                      : ui::EF_NONE;
+  int modifiers = ui::EF_NONE;
+  if (web_wheel.has_precise_scrolling_deltas)
+    modifiers |= ui::EF_PRECISION_SCROLLING_DELTA;
+
+  if (web_wheel.scroll_by_page)
+    modifiers |= ui::EF_SCROLL_BY_PAGE;
+
   ui::MouseWheelEvent wheel_event(
       gfx::Vector2d(web_wheel.delta_x, web_wheel.delta_y), gfx::Point(),
       gfx::Point(), timestamp, modifiers, ui::EF_NONE);

content/browser/renderer_host/input/synthetic_smooth_move_gesture.cc

@@ -33,7 +33,8 @@ SyntheticSmoothMoveGestureParams::SyntheticSmoothMoveGestureParams()
       fling_velocity_y(0),
       prevent_fling(true),
       add_slop(true),
-      precise_scrolling_deltas(false) {}
+      precise_scrolling_deltas(false),
+      scroll_by_page(false) {}
 
 SyntheticSmoothMoveGestureParams::SyntheticSmoothMoveGestureParams(
     const SyntheticSmoothMoveGestureParams& other) = default;
@@ -270,7 +271,8 @@ void SyntheticSmoothMoveGesture::ForwardMouseWheelEvent(
     const base::TimeTicks& timestamp) const {
   blink::WebMouseWheelEvent mouse_wheel_event =
       SyntheticWebMouseWheelEventBuilder::Build(
-          0, 0, delta.x(), delta.y(), 0, params_.precise_scrolling_deltas);
+          0, 0, delta.x(), delta.y(), 0, params_.precise_scrolling_deltas,
+          params_.scroll_by_page);
 
   mouse_wheel_event.SetPositionInWidget(
       current_move_segment_start_position_.x(),

content/browser/renderer_host/input/synthetic_smooth_move_gesture.h

@@ -39,6 +39,7 @@ class CONTENT_EXPORT SyntheticSmoothMoveGestureParams {
   bool prevent_fling;
   bool add_slop;
   bool precise_scrolling_deltas;
+  bool scroll_by_page;
 };
 
 // This class is used as helper class for simulation of scroll and drag.

content/browser/renderer_host/input/synthetic_smooth_scroll_gesture.cc

@@ -51,6 +51,7 @@ bool SyntheticSmoothScrollGesture::InitializeMoveGesture(
     move_params.input_type = GetInputSourceType(gesture_type);
     move_params.add_slop = true;
     move_params.precise_scrolling_deltas = params_.precise_scrolling_deltas;
+    move_params.scroll_by_page = params_.scroll_by_page;
     move_gesture_.reset(new SyntheticSmoothMoveGesture(move_params));
     return true;
   }

content/common/input/synthetic_smooth_scroll_gesture_params.cc

@@ -18,7 +18,8 @@ SyntheticSmoothScrollGestureParams::SyntheticSmoothScrollGestureParams()
       speed_in_pixels_s(kDefaultSpeedInPixelsS),
       fling_velocity_x(0),
       fling_velocity_y(0),
-      precise_scrolling_deltas(false) {}
+      precise_scrolling_deltas(false),
+      scroll_by_page(false) {}
 
 SyntheticSmoothScrollGestureParams::SyntheticSmoothScrollGestureParams(
     const SyntheticSmoothScrollGestureParams& other) = default;

content/common/input/synthetic_smooth_scroll_gesture_params.h

@@ -31,6 +31,7 @@ struct CONTENT_EXPORT SyntheticSmoothScrollGestureParams
   float fling_velocity_x;
   float fling_velocity_y;
   bool precise_scrolling_deltas;
+  bool scroll_by_page;
 
   static const SyntheticSmoothScrollGestureParams* Cast(
       const SyntheticGestureParams* gesture_params);

content/common/input/synthetic_web_input_event_builders.cc

@@ -50,23 +50,27 @@ WebMouseWheelEvent SyntheticWebMouseWheelEventBuilder::Build(
   return result;
 }
 
-WebMouseWheelEvent SyntheticWebMouseWheelEventBuilder::Build(float x,
+WebMouseWheelEvent SyntheticWebMouseWheelEventBuilder::Build(
+    float x,
     float y,
     float dx,
     float dy,
     int modifiers,
-                                                             bool precise) {
-  return Build(x, y, 0, 0, dx, dy, modifiers, precise);
+    bool precise,
+    bool scroll_by_page) {
+  return Build(x, y, 0, 0, dx, dy, modifiers, precise, scroll_by_page);
 }
 
-WebMouseWheelEvent SyntheticWebMouseWheelEventBuilder::Build(float x,
+WebMouseWheelEvent SyntheticWebMouseWheelEventBuilder::Build(
+    float x,
     float y,
     float global_x,
     float global_y,
     float dx,
     float dy,
     int modifiers,
-                                                             bool precise) {
+    bool precise,
+    bool scroll_by_page) {
   WebMouseWheelEvent result(WebInputEvent::kMouseWheel, modifiers,
                             ui::EventTimeForNow());
   result.SetPositionInScreen(global_x, global_y);
@@ -78,6 +82,7 @@ WebMouseWheelEvent SyntheticWebMouseWheelEventBuilder::Build(float x,
   if (dy)
     result.wheel_ticks_y = dy > 0.0f ? 1.0f : -1.0f;
   result.has_precise_scrolling_deltas = precise;
+  result.scroll_by_page = scroll_by_page;
   return result;
 }
 

content/common/input/synthetic_web_input_event_builders.h

@@ -38,7 +38,8 @@ class CONTENT_EXPORT SyntheticWebMouseWheelEventBuilder {
                                          float dx,
                                          float dy,
                                          int modifiers,
-                                         bool precise);
+                                         bool precise,
+                                         bool scroll_by_page = false);
   static blink::WebMouseWheelEvent Build(float x,
                                          float y,
                                          float global_x,
@@ -46,7 +47,8 @@ class CONTENT_EXPORT SyntheticWebMouseWheelEventBuilder {
                                          float dx,
                                          float dy,
                                          int modifiers,
-                                         bool precise);
+                                         bool precise,
+                                         bool scroll_by_page = false);
 };
 
 class CONTENT_EXPORT SyntheticWebKeyboardEventBuilder {

content/common/input_messages.h

@@ -122,6 +122,8 @@ IPC_STRUCT_TRAITS_BEGIN(content::SyntheticSmoothScrollGestureParams)
   IPC_STRUCT_TRAITS_MEMBER(speed_in_pixels_s)
   IPC_STRUCT_TRAITS_MEMBER(fling_velocity_x)
   IPC_STRUCT_TRAITS_MEMBER(fling_velocity_y)
+  IPC_STRUCT_TRAITS_MEMBER(precise_scrolling_deltas)
+  IPC_STRUCT_TRAITS_MEMBER(scroll_by_page)
 IPC_STRUCT_TRAITS_END()
 
 IPC_STRUCT_TRAITS_BEGIN(content::SyntheticPinchGestureParams)

content/renderer/gpu/gpu_benchmarking_extension.cc

@@ -289,7 +289,8 @@ bool BeginSmoothScroll(GpuBenchmarkingContext* context,
                        float start_x,
                        float start_y,
                        float fling_velocity,
-                       bool precise_scrolling_deltas) {
+                       bool precise_scrolling_deltas,
+                       bool scroll_by_page) {
   gfx::Rect rect = context->render_view_impl()->GetWidget()->ViewRect();
   rect -= rect.OffsetFromOrigin();
   if (!rect.Contains(start_x, start_y)) {
@@ -327,6 +328,7 @@ bool BeginSmoothScroll(GpuBenchmarkingContext* context,
   gesture_params.speed_in_pixels_s = speed_in_pixels_s;
   gesture_params.prevent_fling = prevent_fling;
   gesture_params.precise_scrolling_deltas = precise_scrolling_deltas;
+  gesture_params.scroll_by_page = scroll_by_page;
 
   gesture_params.anchor.SetPoint(start_x, start_y);
 
@@ -659,6 +661,7 @@ bool GpuBenchmarking::SmoothScrollBy(gin::Arguments* args) {
   std::string direction = "down";
   float speed_in_pixels_s = 800;
   bool precise_scrolling_deltas = true;
+  bool scroll_by_page = false;
 
   if (!GetOptionalArg(args, &pixels_to_scroll) ||
       !GetOptionalArg(args, &callback) || !GetOptionalArg(args, &start_x) ||
@@ -666,17 +669,23 @@ bool GpuBenchmarking::SmoothScrollBy(gin::Arguments* args) {
       !GetOptionalArg(args, &gesture_source_type) ||
       !GetOptionalArg(args, &direction) ||
       !GetOptionalArg(args, &speed_in_pixels_s) ||
-      !GetOptionalArg(args, &precise_scrolling_deltas)) {
+      !GetOptionalArg(args, &precise_scrolling_deltas) ||
+      !GetOptionalArg(args, &scroll_by_page)) {
     return false;
   }
 
+  // For all touch inputs, always scroll by precise deltas.
   DCHECK(gesture_source_type != SyntheticGestureParams::TOUCH_INPUT ||
          precise_scrolling_deltas);
+  // Scroll by page only for mouse inputs.
+  DCHECK(!scroll_by_page ||
+         gesture_source_type == SyntheticGestureParams::MOUSE_INPUT);
+
   EnsureRemoteInterface();
   return BeginSmoothScroll(&context, args, input_injector_, pixels_to_scroll,
                            callback, gesture_source_type, direction,
                            speed_in_pixels_s, true, start_x, start_y, 0,
-                           precise_scrolling_deltas);
+                           precise_scrolling_deltas, scroll_by_page);
 }
 
 bool GpuBenchmarking::SmoothDrag(gin::Arguments* args) {
@@ -745,7 +754,8 @@ bool GpuBenchmarking::Swipe(gin::Arguments* args) {
   return BeginSmoothScroll(&context, args, input_injector_, -pixels_to_scroll,
                            callback, gesture_source_type, direction,
                            speed_in_pixels_s, false, start_x, start_y,
-                           fling_velocity, true);
+                           fling_velocity, true /* precise_scrolling_deltas */,
+                           false /* scroll_by_page */);
 }
 
 bool GpuBenchmarking::ScrollBounce(gin::Arguments* args) {

third_party/WebKit/LayoutTests/TestExpectations

@@ -2242,6 +2242,7 @@ crbug.com/613672 [ Mac ] virtual/user-activation-v2/fast/events/pointerevents/po
 # regularly on Windows. crbug.com/850964
 crbug.com/613672 [ Mac Win ] virtual/threaded/external/wpt/feature-policy/experimental-features/vertical-scroll-touch-block-manual.tentative.html [ Skip ]
 crbug.com/613672 [ Mac ] fast/events/touch/gesture/gesture-scroll.html [ Skip ]
+crbug.com/613672 [ Mac ] fast/events/touch/gesture/gesture-scroll-by-page.html [ Skip ]
 crbug.com/613672 [ Mac ] fast/events/touch/gesture/gesture-scrollbar-touchpad-fling.html [ Skip ]
 crbug.com/613672 [ Mac ] fast/events/touch/gesture/gesture-scrollbar-touchscreen-fling.html [ Skip ]
 crbug.com/613672 [ Mac ] fast/events/touch/gesture/gesture-scrollbar-mainframe.html [ Skip ]
@@ -2260,6 +2261,7 @@ crbug.com/613672 [ Mac ] fast/events/touch/gesture/touch-gesture-scroll-page-pas
 crbug.com/613672 [ Mac ] fast/events/touch/gesture/touch-gesture-scroll-page-zoomed.html [ Skip ]
 crbug.com/613672 [ Mac ] fast/events/touch/gesture/touch-gesture-scroll-page.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/mouseevent_fractional/fast/events/touch/gesture/gesture-scroll.html [ Skip ]
+crbug.com/613672 [ Mac ] virtual/mouseevent_fractional/fast/events/touch/gesture/gesture-scroll-by-page.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/mouseevent_fractional/fast/events/touch/gesture/gesture-scrollbar-touchpad-fling.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/mouseevent_fractional/fast/events/touch/gesture/gesture-scrollbar-touchscreen-fling.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/mouseevent_fractional/fast/events/touch/gesture/gesture-scrollbar-mainframe.html [ Skip ]
@@ -2278,6 +2280,7 @@ crbug.com/613672 [ Mac ] virtual/mouseevent_fractional/fast/events/touch/gesture
 crbug.com/613672 [ Mac ] virtual/mouseevent_fractional/fast/events/touch/gesture/touch-gesture-scroll-page-zoomed.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/mouseevent_fractional/fast/events/touch/gesture/touch-gesture-scroll-page.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/scroll_customization/fast/events/touch/gesture/gesture-scroll.html [ Skip ]
+crbug.com/613672 [ Mac ] virtual/scroll_customization/fast/events/touch/gesture/gesture-scroll-by-page.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/scroll_customization/fast/events/touch/gesture/gesture-scrollbar-touchpad-fling.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/scroll_customization/fast/events/touch/gesture/gesture-scrollbar-touchscreen-fling.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/scroll_customization/fast/events/touch/gesture/gesture-scrollbar-mainframe.html [ Skip ]
@@ -2296,6 +2299,7 @@ crbug.com/613672 [ Mac ] virtual/scroll_customization/fast/events/touch/gesture/
 crbug.com/613672 [ Mac ] virtual/scroll_customization/fast/events/touch/gesture/touch-gesture-scroll-page-zoomed.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/scroll_customization/fast/events/touch/gesture/touch-gesture-scroll-page.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/user-activation-v2/fast/events/touch/gesture/gesture-scroll.html [ Skip ]
+crbug.com/613672 [ Mac ] virtual/user-activation-v2/fast/events/touch/gesture/gesture-scroll-by-page.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/user-activation-v2/fast/events/touch/gesture/gesture-scrollbar-touchpad-fling.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/user-activation-v2/fast/events/touch/gesture/gesture-scrollbar-touchscreen-fling.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/user-activation-v2/fast/events/touch/gesture/gesture-scrollbar-mainframe.html [ Skip ]
@@ -2314,6 +2318,7 @@ crbug.com/613672 [ Mac ] virtual/user-activation-v2/fast/events/touch/gesture/to
 crbug.com/613672 [ Mac ] virtual/user-activation-v2/fast/events/touch/gesture/touch-gesture-scroll-page-zoomed.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/user-activation-v2/fast/events/touch/gesture/touch-gesture-scroll-page.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/paint-touchaction-rects/fast/events/touch/gesture/gesture-scroll.html [ Skip ]
+crbug.com/613672 [ Mac ] virtual/paint-touchaction-rects/fast/events/touch/gesture/gesture-scroll-by-page.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/paint-touchaction-rects/fast/events/touch/gesture/gesture-scrollbar-mainframe.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/paint-touchaction-rects/fast/events/touch/gesture/gesture-scrollbar.html [ Skip ]
 crbug.com/613672 [ Mac ] virtual/paint-touchaction-rects/fast/events/touch/gesture/touch-gesture-noscroll-body-xhidden.html [ Skip ]

third_party/WebKit/LayoutTests/fast/events/touch/gesture/gesture-scroll-by-page-expected.txt

-This tests gesture scrolling by pages.
-
-On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
-
-
-PASS document.scrollingElement.scrollTop >= window.innerHeight * 0.875 * 2 became true
-PASS successfullyParsed is true
-
-TEST COMPLETE
-

third_party/WebKit/LayoutTests/fast/events/touch/gesture/gesture-scroll-by-page.html

 <!DOCTYPE html>
-<html>
-<head>
-<script src="../../../../resources/js-test.js"></script>
+<script src="../../../../resources/testharness.js"></script>
+<script src="../../../../resources/testharnessreport.js"></script>
+<script src="../../../../resources/gesture-util.js"></script>
 <style type="text/css">
 ::-webkit-scrollbar {
     width: 0px;
@@ -20,8 +20,8 @@
 }
 
 </style>
-</head>
-<body style="margin:0" onload="runTest();">
+
+<body style="margin:0">
 
 <div id="greenbox"></div>
 <div id="redbox"></div>
@@ -29,32 +29,20 @@
 <p id="description"></p>
 <div id="console"></div>
 <script type="text/javascript">
+  // Turn on smooth scrolling.
+  internals.settings.setScrollAnimatorEnabled(true);
 
-function gestureScroll()
-{
-    eventSender.gestureScrollBegin("touchpad", 10, 20);
-    eventSender.gestureScrollUpdate("touchpad", 0, -1, "Page");
-    eventSender.gestureScrollUpdate("touchpad", 0, -2, "Page");
-    eventSender.gestureScrollUpdate("touchpad", 0, 1, "Page");
-    eventSender.gestureScrollEnd("touchpad", 0, 0);
-
-    // see kMinFractionToStepWhenPaging in ScrollableArea.cppP
-    // 2 is the expected number of pages scrolled (-1 + -2 + 1)
-    shouldBecomeEqual("document.scrollingElement.scrollTop >= window.innerHeight * 0.875 * 2", "true", finishJSTest, 1000);
-}
+  var x = 30;
+  var y = 30;
+  var mouse_input = GestureSourceType.MOUSE_INPUT;
 
-jsTestIsAsync = true;
+promise_test (async () => {
+  await smoothScroll(1, x, y, mouse_input, 'down', SPEED_INSTANT, false, true);
+  await smoothScroll(1, x, y, mouse_input, 'down', SPEED_INSTANT, false, true);
+  await waitFor(() => {
+    return document.scrollingElement.scrollTop >= window.innerHeight * 0.875 * 2; })
+});
 
-function runTest()
-{
-    if (window.eventSender) {
-        description('This tests gesture scrolling by pages.');
-        gestureScroll();
-    } else {
-        debug("This test requires DumpRenderTree.  Gesture-scroll the page to validate the implementation.");
-    }
-}
 </script>
 
 </body>
-</html>

third_party/WebKit/LayoutTests/resources/gesture-util.js

@@ -89,7 +89,7 @@ const GestureSourceType = {
 // the synthetic gesture code modified to guarantee the single update behavior.
 const SPEED_INSTANT = 200000;
 
-function smoothScroll(pixels_to_scroll, start_x, start_y, gesture_source_type, direction, speed_in_pixels_s) {
+function smoothScroll(pixels_to_scroll, start_x, start_y, gesture_source_type, direction, speed_in_pixels_s, precise_scrolling_deltas, scroll_by_page) {
   return new Promise((resolve, reject) => {
     if (chrome && chrome.gpuBenchmarking) {
       chrome.gpuBenchmarking.smoothScrollBy(pixels_to_scroll,
@@ -98,7 +98,9 @@ function smoothScroll(pixels_to_scroll, start_x, start_y, gesture_source_type, d
                                             start_y,
                                             gesture_source_type,
                                             direction,
-                                            speed_in_pixels_s);
+                                            speed_in_pixels_s,
+                                            precise_scrolling_deltas,
+                                            scroll_by_page);
     } else {
       reject('This test requires chrome.gpuBenchmarking');
     }

third_party/WebKit/LayoutTests/virtual/threaded/animations/invisible-composited-animations-prevent-scroll.html

@@ -44,6 +44,7 @@ It should not be possible to scroll this content:<br>
         50 /* start_y */,
         GESTURE_SOURCE_TYPE,
         'down',
-        20000 /* speed */);
+        20000 /* speed */,
+        false /* precise_scrolling_deltas */);
   });
 </script>

ui/events/blink/web_input_event.cc

@@ -502,6 +502,8 @@ blink::WebMouseWheelEvent MakeWebMouseWheelEventFromUiEvent(
 
   if (event.flags() & ui::EF_PRECISION_SCROLLING_DELTA)
     webkit_event.has_precise_scrolling_deltas = true;
+  if (event.flags() & ui::EF_SCROLL_BY_PAGE)
+    webkit_event.scroll_by_page = true;
 
   webkit_event.wheel_ticks_x =
       webkit_event.delta_x / MouseWheelEvent::kWheelDelta;

ui/events/event_constants.h

@@ -153,6 +153,9 @@ enum MouseEventFlags {
   EF_PRECISION_SCROLLING_DELTA =     // Indicates this mouse event is from high
   1 << 21,                           // precision touchpad and will come with a
                                      // high precision delta.
+  EF_SCROLL_BY_PAGE = 1 << 22,       // Indicates this mouse event is generated
+                                     // when users is requesting to scroll by
+                                     // pages.
 };
 
 // Result of dispatching an event.