Add ScrollManager class

third_party/WebKit/Source/core/input/EventHandler.cpp

Index: third_party/WebKit/Source/core/input/EventHandler.cpp
diff --git a/third_party/WebKit/Source/core/input/EventHandler.cpp b/third_party/WebKit/Source/core/input/EventHandler.cpp
index 22ff85faa4c717d09a7939f22de3bf7824bf75e5..bad5b0dc36e3628c3abf728963fe111b80484d2d 100644
--- a/third_party/WebKit/Source/core/input/EventHandler.cpp
+++ b/third_party/WebKit/Source/core/input/EventHandler.cpp
@@ -56,7 +56,6 @@
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
-#include "core/frame/TopControls.h"
 #include "core/frame/UseCounter.h"
 #include "core/frame/VisualViewport.h"
 #include "core/html/HTMLDialogElement.h"
@@ -83,8 +82,6 @@
 #include "core/page/Page.h"
 #include "core/page/SpatialNavigation.h"
 #include "core/page/TouchAdjustment.h"
-#include "core/page/scrolling/OverscrollController.h"
-#include "core/page/scrolling/RootScroller.h"
 #include "core/page/scrolling/ScrollState.h"
 #include "core/paint/PaintLayer.h"
 #include "core/style/ComputedStyle.h"
@@ -143,47 +140,6 @@ bool shouldRefetchEventTarget(const MouseEventWithHitTestResults& mev)
     return targetNode->isShadowRoot() && isHTMLInputElement(toShadowRoot(targetNode)->host());
 }
 
-// TODO(bokan): This method can go away once all scrolls happen through the
-// scroll customization path.
-void computeScrollChainForSingleNode(Node& node, std::deque<int>& scrollChain)
-{
-    scrollChain.clear();
-
-    ASSERT(node.layoutObject());
-    Element* element = toElement(&node);
-
-    scrollChain.push_front(DOMNodeIds::idForNode(element));
-}
-
-void recomputeScrollChain(const LocalFrame& frame, const Node& startNode,
-    std::deque<int>& scrollChain)
-{
-    scrollChain.clear();
-
-    ASSERT(startNode.layoutObject());
-    LayoutBox* curBox = startNode.layoutObject()->enclosingBox();
-
-    // Scrolling propagates along the containing block chain.
-    while (curBox && !curBox->isLayoutView()) {
-        Node* curNode = curBox->node();
-        // FIXME: this should reject more elements, as part of crbug.com/410974.
-        if (curNode && curNode->isElementNode()) {
-            Element* curElement = toElement(curNode);
-            if (curElement == frame.document()->scrollingElement())
-                break;
-            scrollChain.push_front(DOMNodeIds::idForNode(curElement));
-        }
-        curBox = curBox->containingBlock();
-    }
-    // TODO(tdresser): this should sometimes be excluded, as part of crbug.com/410974.
-    // We need to ensure that the scrollingElement is always part of
-    // the scroll chain. In quirks mode, when the scrollingElement is
-    // the body, some elements may use the documentElement as their
-    // containingBlock, so we ensure the scrollingElement is added
-    // here.
-    scrollChain.push_front(DOMNodeIds::idForNode(frame.document()->scrollingElement()));
-}
-
 } // namespace
 
 using namespace HTMLNames;
@@ -249,19 +205,16 @@ EventHandler::EventHandler(LocalFrame* frame)
     , m_mouseDownMayStartAutoscroll(false)
     , m_fakeMouseMoveEventTimer(this, &EventHandler::fakeMouseMoveEventTimerFired)
     , m_svgPan(false)
-    , m_resizeScrollableArea(nullptr)
     , m_eventHandlerWillResetCapturingMouseEventsNode(0)
     , m_clickCount(0)
     , m_shouldOnlyFireDragOverEvent(false)
     , m_mousePositionIsUnknown(true)
     , m_mouseDownTimestamp(0)
     , m_pointerEventManager(frame)
-    , m_scrollGestureHandlingNode(nullptr)
-    , m_lastGestureScrollOverWidget(false)
+    , m_scrollManager(frame)
     , m_longTapShouldInvokeContextMenu(false)
     , m_activeIntervalTimer(this, &EventHandler::activeIntervalTimerFired)
     , m_lastShowPressTimestamp(0)
-    , m_deltaConsumedForScrollSequence(false)
 {
 }
 
@@ -274,7 +227,6 @@ DEFINE_TRACE(EventHandler)
 {
     visitor->trace(m_frame);
     visitor->trace(m_mousePressNode);
-    visitor->trace(m_resizeScrollableArea);
     visitor->trace(m_capturingMouseEventsNode);
     visitor->trace(m_nodeUnderMouse);
     visitor->trace(m_lastMouseMoveEventSubframe);
@@ -282,12 +234,10 @@ DEFINE_TRACE(EventHandler)
     visitor->trace(m_clickNode);
     visitor->trace(m_dragTarget);
     visitor->trace(m_frameSetBeingResized);
-    visitor->trace(m_scrollbarHandlingScrollGesture);
-    visitor->trace(m_scrollGestureHandlingNode);
-    visitor->trace(m_previousGestureScrolledNode);
     visitor->trace(m_lastDeferredTapElement);
     visitor->trace(m_selectionController);
     visitor->trace(m_pointerEventManager);
+    visitor->trace(m_scrollManager);
 }
 
 DragState& EventHandler::dragState()
@@ -302,7 +252,6 @@ void EventHandler::clear()
     m_cursorUpdateTimer.stop();
     m_fakeMouseMoveEventTimer.stop();
     m_activeIntervalTimer.stop();
-    m_resizeScrollableArea = nullptr;
     m_nodeUnderMouse = nullptr;
     m_lastMouseMoveEventSubframe = nullptr;
     m_lastScrollbarUnderMouse = nullptr;
@@ -319,10 +268,8 @@ void EventHandler::clear()
     m_mousePressed = false;
     m_capturesDragging = false;
     m_capturingMouseEventsNode = nullptr;
-    clearGestureScrollState();
-    m_lastGestureScrollOverWidget = false;
-    m_scrollbarHandlingScrollGesture = nullptr;
     m_pointerEventManager.clear();
+    m_scrollManager.clear();
     m_mouseDownMayStartDrag = false;
     m_lastShowPressTimestamp = 0;
     m_lastDeferredTapElement = nullptr;
@@ -333,7 +280,6 @@ void EventHandler::clear()
     m_mouseDownTimestamp = 0;
     m_longTapShouldInvokeContextMenu = false;
     m_dragStartPos = LayoutPoint();
-    m_offsetFromResizeCorner = LayoutSize();
     m_mouseDown = PlatformMouseEvent();
 }
 
@@ -483,8 +429,8 @@ WebInputEventResult EventHandler::handleMouseDraggedEvent(const MouseEventWithHi
 
     m_mouseDownMayStartDrag = false;
 
-    if (m_mouseDownMayStartAutoscroll && !panScrollInProgress()) {
-        if (AutoscrollController* controller = autoscrollController()) {
+    if (m_mouseDownMayStartAutoscroll && !m_scrollManager.panScrollInProgress()) {
+        if (AutoscrollController* controller = m_scrollManager.autoscrollController()) {
             controller->startAutoscrollForSelection(layoutObject);
             m_mouseDownMayStartAutoscroll = false;
         }
@@ -501,9 +447,9 @@ void EventHandler::updateSelectionForMouseDrag()
 
 WebInputEventResult EventHandler::handleMouseReleaseEvent(const MouseEventWithHitTestResults& event)
 {
-    AutoscrollController* controller = autoscrollController();
+    AutoscrollController* controller = m_scrollManager.autoscrollController();
     if (controller && controller->autoscrollInProgress())
-        stopAutoscroll();
+        m_scrollManager.stopAutoscroll();
 
     // Used to prevent mouseMoveEvent from initiating a drag before
     // the mouse is pressed again.
@@ -521,7 +467,7 @@ void EventHandler::startPanScrolling(LayoutObject* layoutObject)
 {
     if (!layoutObject->isBox())
         return;
-    AutoscrollController* controller = autoscrollController();
+    AutoscrollController* controller = m_scrollManager.autoscrollController();
     if (!controller)
         return;
     controller->startPanScrolling(toLayoutBox(layoutObject), lastKnownMousePosition());
@@ -530,18 +476,6 @@ void EventHandler::startPanScrolling(LayoutObject* layoutObject)
 
 #endif // OS(WIN)
 
-AutoscrollController* EventHandler::autoscrollController() const
-{
-    if (Page* page = m_frame->page())
-        return &page->autoscrollController();
-    return nullptr;
-}
-
-bool EventHandler::panScrollInProgress() const
-{
-    return autoscrollController() && autoscrollController()->panScrollInProgress();
-}
-
 HitTestResult EventHandler::hitTestResultAtPoint(const LayoutPoint& point, HitTestRequest::HitTestRequestType hitType, const LayoutSize& padding)
 {
     TRACE_EVENT0("blink", "EventHandler::hitTestResultAtPoint");
@@ -584,186 +518,14 @@ HitTestResult EventHandler::hitTestResultAtPoint(const LayoutPoint& point, HitTe
 
 void EventHandler::stopAutoscroll()
 {
-    if (AutoscrollController* controller = autoscrollController())
-        controller->stopAutoscroll();
-}
-
-ScrollResult EventHandler::scrollBox(LayoutBox* box,
-    ScrollGranularity granularity, const FloatSize& delta,
-    const FloatPoint& position, const FloatSize& velocity,
-    bool* wasRootScroller)
-{
-    ASSERT(box);
-    Node* node = box->node();
-
-    // If there's no ApplyScroll callback on the element, scroll as usuall in
-    // the non-scroll-customization case.
-    if (!node || !node->isElementNode() || !toElement(node)->getApplyScroll()) {
-        *wasRootScroller = false;
-        return box->scroll(granularity, delta);
-    }
-
-    // Viewport actions should only happen when scrolling an element in the
-    // main frame.
-    ASSERT(m_frame->isMainFrame());
-
-    // If there is an ApplyScroll callback, its because we placed one on the
-    // root scroller to control top controls and overscroll. Invoke a scroll
-    // using parts of the scroll customization framework on just this element.
-    computeScrollChainForSingleNode(*node, m_currentScrollChain);
-
-    OwnPtr<ScrollStateData> scrollStateData = adoptPtr(new ScrollStateData());
-    scrollStateData->delta_x = delta.width();
-    scrollStateData->delta_y = delta.height();
-    scrollStateData->position_x = position.x();
-    scrollStateData->position_y = position.y();
-    // TODO(bokan): delta_granularity is meant to be the number of pixels per
-    // unit of delta but we can't determine that until we get to the area we'll
-    // scroll. This is a hack, we stuff the enum into the double value for
-    // now.
-    scrollStateData->delta_granularity = static_cast<double>(granularity);
-    scrollStateData->velocity_x = velocity.width();
-    scrollStateData->velocity_y = velocity.height();
-    scrollStateData->should_propagate = false;
-    scrollStateData->is_in_inertial_phase = false;
-    scrollStateData->from_user_input = true;
-    scrollStateData->delta_consumed_for_scroll_sequence = false;
-    ScrollState* scrollState =
-        ScrollState::create(std::move(scrollStateData));
-
-    customizedScroll(*node, *scrollState);
-
-    ScrollResult result(
-        scrollState->deltaX() != delta.width(),
-        scrollState->deltaY() != delta.height(),
-        scrollState->deltaX(),
-        scrollState->deltaY());
-
-    *wasRootScroller = true;
-    m_currentScrollChain.clear();
-
-    return result;
-}
-
-ScrollResult EventHandler::physicalScroll(ScrollGranularity granularity,
-    const FloatSize& delta, const FloatPoint& position,
-    const FloatSize& velocity, Node* startNode, Node** stopNode, bool* consumed)
-{
-    if (consumed)
-        *consumed = false;
-    if (delta.isZero())
-        return ScrollResult();
-
-    Node* node = startNode;
-    ASSERT(node && node->layoutObject());
-
-    m_frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();
-
-    ScrollResult result;
-
-    LayoutBox* curBox = node->layoutObject()->enclosingBox();
-    while (curBox) {
-        // If we're at the stopNode, we should try to scroll it but we shouldn't
-        // chain past it.
-        bool shouldStopChaining =
-            stopNode && *stopNode && curBox->node() == *stopNode;
-        bool wasRootScroller = false;
-
-        result = scrollBox(
-            curBox,
-            granularity,
-            delta,
-            position,
-            velocity,
-            &wasRootScroller);
-
-        if (result.didScroll() && stopNode)
-            *stopNode = curBox->node();
-
-        if (result.didScroll() || shouldStopChaining) {
-            setFrameWasScrolledByUser();
-            if (consumed)
-                *consumed = true;
-            return result;
-        } else if (wasRootScroller) {
-            // Don't try to chain past the root scroller, even if there's
-            // eligible ancestors.
-            break;
-        }
-
-        curBox = curBox->containingBlock();
-    }
-
-    return result;
-}
-
-bool EventHandler::logicalScroll(ScrollDirection direction, ScrollGranularity granularity, Node* startNode)
-{
-    Node* node = startNode;
-
-    if (!node)
-        node = m_frame->document()->focusedElement();
-
-    if (!node)
-        node = m_mousePressNode.get();
-
-    if ((!node || !node->layoutObject()) && m_frame->view() && !m_frame->view()->layoutViewItem().isNull())
-        node = m_frame->view()->layoutViewItem().node();
-
-    if (!node)
-        return false;
-
-    m_frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();
-
-    LayoutBox* curBox = node->layoutObject()->enclosingBox();
-    while (curBox) {
-        ScrollDirectionPhysical physicalDirection = toPhysicalDirection(
-            direction, curBox->isHorizontalWritingMode(), curBox->style()->isFlippedBlocksWritingMode());
-
-        ScrollResult result = curBox->scroll(granularity, toScrollDelta(physicalDirection, 1));
-
-        if (result.didScroll()) {
-            setFrameWasScrolledByUser();
-            return true;
-        }
-
-        curBox = curBox->containingBlock();
-    }
-
-    return false;
-}
-
-void EventHandler::customizedScroll(const Node& startNode, ScrollState& scrollState)
-{
-    if (scrollState.fullyConsumed())
-        return;
-
-    if (scrollState.deltaX() || scrollState.deltaY())
-        m_frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();
-
-    if (m_currentScrollChain.empty())
-        recomputeScrollChain(*m_frame, startNode, m_currentScrollChain);
-    scrollState.setScrollChain(m_currentScrollChain);
-
-    scrollState.distributeToScrollChainDescendant();
+    m_scrollManager.stopAutoscroll();
 }
 
 // TODO(bokan): This should be merged with logicalScroll assuming
 // defaultSpaceEventHandler's chaining scroll can be done crossing frames.
 bool EventHandler::bubblingScroll(ScrollDirection direction, ScrollGranularity granularity, Node* startingNode)
 {
-    // The layout needs to be up to date to determine if we can scroll. We may be
-    // here because of an onLoad event, in which case the final layout hasn't been performed yet.
-    m_frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();
-    // FIXME: enable scroll customization in this case. See crbug.com/410974.
-    if (logicalScroll(direction, granularity, startingNode))
-        return true;
-
-    Frame* parentFrame = m_frame->tree().parent();
-    if (!parentFrame || !parentFrame->isLocalFrame())
-        return false;
-    // FIXME: Broken for OOPI.
-    return toLocalFrame(parentFrame)->eventHandler().bubblingScroll(direction, granularity, m_frame->deprecatedLocalOwner());
+    return m_scrollManager.bubblingScroll(direction, granularity, startingNode, m_mousePressNode);
 }
 
 IntPoint EventHandler::lastKnownMousePosition() const
@@ -858,13 +620,13 @@ void EventHandler::updateCursor()
 
 OptionalCursor EventHandler::selectCursor(const HitTestResult& result)
 {
-    if (m_resizeScrollableArea && m_resizeScrollableArea->inResizeMode())
+    if (m_scrollManager.inResizeMode())
         return NoCursorChange;
 
     Page* page = m_frame->page();
     if (!page)
         return NoCursorChange;
-    if (panScrollInProgress())
+    if (m_scrollManager.panScrollInProgress())
         return NoCursorChange;
 
     Node* node = result.innerPossiblyPseudoNode();
@@ -1097,8 +859,8 @@ WebInputEventResult EventHandler::handleMousePressEvent(const PlatformMouseEvent
 #if OS(WIN)
     // We store whether pan scrolling is in progress before calling stopAutoscroll()
     // because it will set m_autoscrollType to NoAutoscroll on return.
-    bool isPanScrollInProgress = panScrollInProgress();
-    stopAutoscroll();
+    bool isPanScrollInProgress = m_scrollManager.panScrollInProgress();
+    m_scrollManager.stopAutoscroll();
     if (isPanScrollInProgress) {
         // We invalidate the click when exiting pan scrolling so that we don't inadvertently navigate
         // away from the current page (e.g. the click was on a hyperlink). See <rdar://problem/6095023>.
@@ -1119,9 +881,7 @@ WebInputEventResult EventHandler::handleMousePressEvent(const PlatformMouseEvent
         PaintLayer* layer = mev.innerNode()->layoutObject() ? mev.innerNode()->layoutObject()->enclosingLayer() : nullptr;
         IntPoint p = view->rootFrameToContents(mouseEvent.position());
         if (layer && layer->getScrollableArea() && layer->getScrollableArea()->isPointInResizeControl(p, ResizerForPointer)) {
-            m_resizeScrollableArea = layer->getScrollableArea();
-            m_resizeScrollableArea->setInResizeMode(true);
-            m_offsetFromResizeCorner = LayoutSize(m_resizeScrollableArea->offsetFromResizeCorner(p));
+            m_scrollManager.setResizeScrollableArea(layer, p);
             return WebInputEventResult::HandledSystem;
         }
     }
@@ -1292,8 +1052,8 @@ WebInputEventResult EventHandler::handleMouseMoveOrLeaveEvent(const PlatformMous
 
     Scrollbar* scrollbar = nullptr;
 
-    if (m_resizeScrollableArea && m_resizeScrollableArea->inResizeMode()) {
-        m_resizeScrollableArea->resize(mev.event(), m_offsetFromResizeCorner);
+    if (m_scrollManager.inResizeMode()) {
+        m_scrollManager.resize(mev.event());
     } else {
         if (!scrollbar)
             scrollbar = mev.scrollbar();
@@ -1461,10 +1221,7 @@ WebInputEventResult EventHandler::handleMouseReleaseEvent(const PlatformMouseEve
         }
     }
 
-    if (m_resizeScrollableArea) {
-        m_resizeScrollableArea->setInResizeMode(false);
-        m_resizeScrollableArea = nullptr;
-    }
+    m_scrollManager.clearResizeScrollableArea(false);
 
     if (eventResult == WebInputEventResult::NotHandled)
         eventResult = handleMouseReleaseEvent(mev);
@@ -1559,7 +1316,7 @@ WebInputEventResult EventHandler::updateDragAndDrop(const PlatformMouseEvent& ev
     if (newTarget && newTarget->isTextNode())
         newTarget = FlatTreeTraversal::parent(*newTarget);
 
-    if (AutoscrollController* controller = autoscrollController())
+    if (AutoscrollController* controller = m_scrollManager.autoscrollController())
         controller->updateDragAndDrop(newTarget, event.position(), event.timestamp());
 
     if (m_dragTarget != newTarget) {
@@ -1647,7 +1404,7 @@ WebInputEventResult EventHandler::performDragAndDrop(const PlatformMouseEvent& e
 
 void EventHandler::clearDragState()
 {
-    stopAutoscroll();
+    m_scrollManager.stopAutoscroll();
     m_dragTarget = nullptr;
     m_capturingMouseEventsNode = nullptr;
     m_shouldOnlyFireDragOverEvent = false;
@@ -1889,7 +1646,7 @@ WebInputEventResult EventHandler::handleWheelEvent(const PlatformWheelEvent& eve
     if (subframe) {
         WebInputEventResult result = subframe->eventHandler().handleWheelEvent(event);
         if (result != WebInputEventResult::NotHandled) {
-            setFrameWasScrolledByUser();
+            m_scrollManager.setFrameWasScrolledByUser();
             return result;
         }
         // TODO(dtapuska): Remove this once wheel gesture scroll has
@@ -1957,7 +1714,7 @@ void EventHandler::defaultWheelEventHandler(Node* startNode, WheelEvent* wheelEv
     // FIXME: enable scroll customization in this case. See crbug.com/410974.
     bool consumed = false;
 
-    physicalScroll(
+    m_scrollManager.physicalScroll(
         granularity,
         delta,
         FloatPoint(),
@@ -2035,17 +1792,10 @@ WebInputEventResult EventHandler::handleGestureEventInFrame(const GestureEventWi
     ASSERT(!targetedEvent.event().isScrollEvent());
 
     Node* eventTarget = targetedEvent.hitTestResult().innerNode();
-    Scrollbar* scrollbar = targetedEvent.hitTestResult().scrollbar();
     const PlatformGestureEvent& gestureEvent = targetedEvent.event();
 
-    if (scrollbar) {
-        bool shouldUpdateCapture = false;
-        if (scrollbar->gestureEvent(gestureEvent, &shouldUpdateCapture)) {
-            if (shouldUpdateCapture)
-                m_scrollbarHandlingScrollGesture = scrollbar;
-            return WebInputEventResult::HandledSuppressed;
-        }
-    }
+    if (m_scrollManager.canHandleGestureEvent(targetedEvent))
+        return WebInputEventResult::HandledSuppressed;
 
     if (eventTarget) {
         GestureEvent* gestureDomEvent = GestureEvent::create(eventTarget->document().domWindow(), gestureEvent);
@@ -2087,74 +1837,7 @@ WebInputEventResult EventHandler::handleGestureScrollEvent(const PlatformGesture
 {
     TRACE_EVENT0("input", "EventHandler::handleGestureScrollEvent");
 
-    Node* eventTarget = nullptr;
-    Scrollbar* scrollbar = nullptr;
-    if (gestureEvent.type() != PlatformEvent::GestureScrollBegin) {
-        scrollbar = m_scrollbarHandlingScrollGesture.get();
-        eventTarget = m_scrollGestureHandlingNode.get();
-    }
-
-    if (!eventTarget) {
-        Document* document = m_frame->document();
-        if (document->layoutViewItem().isNull())
-            return WebInputEventResult::NotHandled;
-
-        FrameView* view = m_frame->view();
-        LayoutPoint viewPoint = view->rootFrameToContents(gestureEvent.position());
-        HitTestRequest request(HitTestRequest::ReadOnly);
-        HitTestResult result(request, viewPoint);
-        document->layoutViewItem().hitTest(result);
-
-        eventTarget = result.innerNode();
-
-        m_lastGestureScrollOverWidget = result.isOverWidget();
-        m_scrollGestureHandlingNode = eventTarget;
-        m_previousGestureScrolledNode = nullptr;
-
-        if (!scrollbar)
-            scrollbar = result.scrollbar();
-    }
-
-    if (scrollbar) {
-        bool shouldUpdateCapture = false;
-        if (scrollbar->gestureEvent(gestureEvent, &shouldUpdateCapture)) {
-            if (shouldUpdateCapture)
-                m_scrollbarHandlingScrollGesture = scrollbar;
-            return WebInputEventResult::HandledSuppressed;
-        }
-        m_scrollbarHandlingScrollGesture = nullptr;
-    }
-
-    if (eventTarget) {
-        if (handleScrollGestureOnResizer(eventTarget, gestureEvent))
-            return WebInputEventResult::HandledSuppressed;
-
-        GestureEvent* gestureDomEvent = GestureEvent::create(eventTarget->document().domWindow(), gestureEvent);
-        if (gestureDomEvent) {
-            DispatchEventResult gestureDomEventResult = eventTarget->dispatchEvent(gestureDomEvent);
-            if (gestureDomEventResult != DispatchEventResult::NotCanceled) {
-                ASSERT(gestureDomEventResult != DispatchEventResult::CanceledByEventHandler);
-                return toWebInputEventResult(gestureDomEventResult);
-            }
-        }
-    }
-
-    switch (gestureEvent.type()) {
-    case PlatformEvent::GestureScrollBegin:
-        return handleGestureScrollBegin(gestureEvent);
-    case PlatformEvent::GestureScrollUpdate:
-        return handleGestureScrollUpdate(gestureEvent);
-    case PlatformEvent::GestureScrollEnd:
-        return handleGestureScrollEnd(gestureEvent);
-    case PlatformEvent::GestureFlingStart:
-    case PlatformEvent::GesturePinchBegin:
-    case PlatformEvent::GesturePinchEnd:
-    case PlatformEvent::GesturePinchUpdate:
-        return WebInputEventResult::NotHandled;
-    default:
-        ASSERT_NOT_REACHED();
-        return WebInputEventResult::NotHandled;
-    }
+    return m_scrollManager.handleGestureScrollEvent(gestureEvent);
 }
 
 WebInputEventResult EventHandler::handleGestureTap(const GestureEventWithHitTestResults& targetedEvent)
@@ -2317,235 +2000,14 @@ WebInputEventResult EventHandler::handleGestureLongTap(const GestureEventWithHit
     return WebInputEventResult::NotHandled;
 }
 
-bool EventHandler::handleScrollGestureOnResizer(Node* eventTarget, const PlatformGestureEvent& gestureEvent)
-{
-    if (gestureEvent.type() == PlatformEvent::GestureScrollBegin) {
-        PaintLayer* layer = eventTarget->layoutObject() ? eventTarget->layoutObject()->enclosingLayer() : nullptr;
-        IntPoint p = m_frame->view()->rootFrameToContents(gestureEvent.position());
-        if (layer && layer->getScrollableArea() && layer->getScrollableArea()->isPointInResizeControl(p, ResizerForTouch)) {
-            m_resizeScrollableArea = layer->getScrollableArea();
-            m_resizeScrollableArea->setInResizeMode(true);
-            m_offsetFromResizeCorner = LayoutSize(m_resizeScrollableArea->offsetFromResizeCorner(p));
-            return true;
-        }
-    } else if (gestureEvent.type() == PlatformEvent::GestureScrollUpdate) {
-        if (m_resizeScrollableArea && m_resizeScrollableArea->inResizeMode()) {
-            m_resizeScrollableArea->resize(gestureEvent, m_offsetFromResizeCorner);
-            return true;
-        }
-    } else if (gestureEvent.type() == PlatformEvent::GestureScrollEnd) {
-        if (m_resizeScrollableArea && m_resizeScrollableArea->inResizeMode()) {
-            m_resizeScrollableArea->setInResizeMode(false);
-            m_resizeScrollableArea = nullptr;
-            return false;
-        }
-    }
-
-    return false;
-}
-
-WebInputEventResult EventHandler::passScrollGestureEventToWidget(const PlatformGestureEvent& gestureEvent, LayoutObject* layoutObject)
-{
-    ASSERT(gestureEvent.isScrollEvent());
-
-    if (!m_lastGestureScrollOverWidget || !layoutObject || !layoutObject->isLayoutPart())
-        return WebInputEventResult::NotHandled;
-
-    Widget* widget = toLayoutPart(layoutObject)->widget();
-
-    if (!widget || !widget->isFrameView())
-        return WebInputEventResult::NotHandled;
-
-    return toFrameView(widget)->frame().eventHandler().handleGestureScrollEvent(gestureEvent);
-}
-
 WebInputEventResult EventHandler::handleGestureScrollEnd(const PlatformGestureEvent& gestureEvent)

[mustaq, 2016/05/31 16:04:11]

There seems to be many "op-op" wrappers to a corresponding scollManager
functions. This is an indication that adding a public
EventHandler::scrollMamanger() (return m_scrollManager} may be a better idea.

[Navid Zolghadr, 2016/05/31 16:11:16]

I thought that too. But I wanted to have that sort of APIs more clear with this
op-op way in EventHandler. This way it is clear that these APIs from
EventHandler are being called in different places in the code. In other words no
class accesses the *Manager class APIs directly and outside of this folder (or
outside of its frame). This way it is more clear what APIs of a frame are
exposed to other frames/classes. Is that reasonable?

[bokan, 2016/05/31 19:39:13]

I think it's fine to make EventHandler the "interface" and let it delegate to
the various managers. At the least, this is a good start to breaking everything
apart for more cleanup down the line. Once we've broken up EventHandler, maybe
we'll decide that different managers should have different visibility to the
higher levels but I think that's premature for now so I'm fine with this as-is.

[mustaq, 2016/05/31 20:20:10]

+1 on deferring the visibility of the sub-units, but I would ask for a TODO so
that it doesn't fall through the cracks.

[Navid Zolghadr, 2016/06/01 17:36:43]

Done.

 {
-    Node* node = m_scrollGestureHandlingNode;
-
-    if (node) {
-        passScrollGestureEventToWidget(gestureEvent, node->layoutObject());
-        if (RuntimeEnabledFeatures::scrollCustomizationEnabled()) {
-            OwnPtr<ScrollStateData> scrollStateData = adoptPtr(new ScrollStateData());
-            scrollStateData->is_ending = true;
-            scrollStateData->is_in_inertial_phase = gestureEvent.inertialPhase() == ScrollInertialPhaseMomentum;
-            scrollStateData->from_user_input = true;
-            scrollStateData->is_direct_manipulation = true;
-            scrollStateData->delta_consumed_for_scroll_sequence = m_deltaConsumedForScrollSequence;
-            ScrollState* scrollState = ScrollState::create(std::move(scrollStateData));
-            customizedScroll(*node, *scrollState);
-        }
-    }
-
-    clearGestureScrollState();
-    return WebInputEventResult::NotHandled;
-}
-
-WebInputEventResult EventHandler::handleGestureScrollBegin(const PlatformGestureEvent& gestureEvent)
-{
-    Document* document = m_frame->document();
-    if (document->layoutViewItem().isNull())
-        return WebInputEventResult::NotHandled;
-
-    FrameView* view = m_frame->view();
-    if (!view)
-        return WebInputEventResult::NotHandled;
-
-    // If there's no layoutObject on the node, send the event to the nearest ancestor with a layoutObject.
-    // Needed for <option> and <optgroup> elements so we can touch scroll <select>s
-    while (m_scrollGestureHandlingNode && !m_scrollGestureHandlingNode->layoutObject())
-        m_scrollGestureHandlingNode = m_scrollGestureHandlingNode->parentOrShadowHostNode();
-
-    if (!m_scrollGestureHandlingNode) {
-        if (RuntimeEnabledFeatures::scrollCustomizationEnabled())
-            m_scrollGestureHandlingNode = m_frame->document()->documentElement();
-        else
-            return WebInputEventResult::NotHandled;
-    }
-    ASSERT(m_scrollGestureHandlingNode);
-
-    passScrollGestureEventToWidget(gestureEvent, m_scrollGestureHandlingNode->layoutObject());
-    if (RuntimeEnabledFeatures::scrollCustomizationEnabled()) {
-        m_currentScrollChain.clear();
-        OwnPtr<ScrollStateData> scrollStateData = adoptPtr(new ScrollStateData());
-        scrollStateData->position_x = gestureEvent.position().x();
-        scrollStateData->position_y = gestureEvent.position().y();
-        scrollStateData->is_beginning = true;
-        scrollStateData->from_user_input = true;
-        scrollStateData->delta_consumed_for_scroll_sequence = m_deltaConsumedForScrollSequence;
-        ScrollState* scrollState = ScrollState::create(std::move(scrollStateData));
-        customizedScroll(*m_scrollGestureHandlingNode.get(), *scrollState);
-    } else {
-        if (m_frame->isMainFrame())
-            m_frame->host()->topControls().scrollBegin();
-    }
-    return WebInputEventResult::HandledSystem;
-}
-
-bool EventHandler::isRootScroller(const Node& node) const
-{
-    // The root scroller is the one Element on the page designated to perform
-    // "viewport actions" like top controls movement and overscroll glow.
-    if (!frameHost() || !frameHost()->rootScroller())
-        return false;
-
-    return frameHost()->rootScroller()->get() == &node;
-}
-
-WebInputEventResult EventHandler::handleGestureScrollUpdate(const PlatformGestureEvent& gestureEvent)
-{
-    ASSERT(gestureEvent.type() == PlatformEvent::GestureScrollUpdate);
-
-    // Negate the deltas since the gesture event stores finger movement and
-    // scrolling occurs in the direction opposite the finger's movement
-    // direction. e.g. Finger moving up has negative event delta but causes the
-    // page to scroll down causing positive scroll delta.
-    FloatSize delta(-gestureEvent.deltaX(), -gestureEvent.deltaY());
-    FloatSize velocity(-gestureEvent.velocityX(), -gestureEvent.velocityY());
-    if (delta.isZero())
-        return WebInputEventResult::NotHandled;
-
-    ScrollGranularity granularity = gestureEvent.deltaUnits();
-    Node* node = m_scrollGestureHandlingNode.get();
-
-    // Scroll customization is only available for touch.
-    bool handleScrollCustomization = RuntimeEnabledFeatures::scrollCustomizationEnabled() && gestureEvent.source() == PlatformGestureSourceTouchscreen;
-    if (node) {
-        LayoutObject* layoutObject = node->layoutObject();
-        if (!layoutObject)
-            return WebInputEventResult::NotHandled;
-
-        // Try to send the event to the correct view.
-        WebInputEventResult result = passScrollGestureEventToWidget(gestureEvent, layoutObject);
-        if (result != WebInputEventResult::NotHandled) {
-            if (gestureEvent.preventPropagation()
-                && !RuntimeEnabledFeatures::scrollCustomizationEnabled()) {
-                // This is an optimization which doesn't apply with
-                // scroll customization enabled.
-                m_previousGestureScrolledNode = m_scrollGestureHandlingNode;
-            }
-            // FIXME: we should allow simultaneous scrolling of nested
-            // iframes along perpendicular axes. See crbug.com/466991.
-            m_deltaConsumedForScrollSequence = true;
-            return result;
-        }
-
-        if (handleScrollCustomization) {
-            OwnPtr<ScrollStateData> scrollStateData = adoptPtr(new ScrollStateData());
-            scrollStateData->delta_x = delta.width();
-            scrollStateData->delta_y = delta.height();
-            scrollStateData->delta_granularity = ScrollByPrecisePixel;
-            scrollStateData->velocity_x = velocity.width();
-            scrollStateData->velocity_y = velocity.height();
-            scrollStateData->should_propagate = !gestureEvent.preventPropagation();
-            scrollStateData->is_in_inertial_phase = gestureEvent.inertialPhase() == ScrollInertialPhaseMomentum;
-            scrollStateData->from_user_input = true;
-            scrollStateData->delta_consumed_for_scroll_sequence = m_deltaConsumedForScrollSequence;
-            ScrollState* scrollState = ScrollState::create(std::move(scrollStateData));
-            if (m_previousGestureScrolledNode) {
-                // The ScrollState needs to know what the current
-                // native scrolling element is, so that for an
-                // inertial scroll that shouldn't propagate, only the
-                // currently scrolling element responds.
-                ASSERT(m_previousGestureScrolledNode->isElementNode());
-                scrollState->setCurrentNativeScrollingElement(toElement(m_previousGestureScrolledNode.get()));
-            }
-            customizedScroll(*node, *scrollState);
-            m_previousGestureScrolledNode = scrollState->currentNativeScrollingElement();
-            m_deltaConsumedForScrollSequence = scrollState->deltaConsumedForScrollSequence();
-            if (scrollState->deltaX() != delta.width()
-                || scrollState->deltaY() != delta.height()) {
-                setFrameWasScrolledByUser();
-                return WebInputEventResult::HandledSystem;
-            }
-        } else {
-            Node* stopNode = nullptr;
-            if (gestureEvent.preventPropagation())
-                stopNode = m_previousGestureScrolledNode.get();
-
-            bool consumed = false;
-            ScrollResult result = physicalScroll(
-                granularity,
-                delta,
-                FloatPoint(gestureEvent.position()),
-                velocity,
-                node,
-                &stopNode,
-                &consumed);
-
-            if (gestureEvent.preventPropagation())
-                m_previousGestureScrolledNode = stopNode;
-
-            if ((!stopNode || !isRootScroller(*stopNode)) && frameHost()) {
-                frameHost()->overscrollController().resetAccumulated(
-                    result.didScrollX, result.didScrollY);
-            }
-
-            if (consumed)
-                return WebInputEventResult::HandledSystem;
-        }
-    }
-
-    return WebInputEventResult::NotHandled;
-}
-
-void EventHandler::clearGestureScrollState()
-{
-    m_scrollGestureHandlingNode = nullptr;
-    m_previousGestureScrolledNode = nullptr;
-    m_deltaConsumedForScrollSequence = false;
-    m_currentScrollChain.clear();
-
-    if (FrameHost* host = frameHost()) {
-        bool resetX = true;
-        bool resetY = true;
-        host->overscrollController().resetAccumulated(resetX, resetY);
-    }
+    return m_scrollManager.handleGestureScrollEnd(gestureEvent);
 }
 
 bool EventHandler::isScrollbarHandlingGestures() const
 {
-    return m_scrollbarHandlingScrollGesture.get();
+    return m_scrollManager.isScrollbarHandlingGestures();
 }
 
 bool EventHandler::shouldApplyTouchAdjustment(const PlatformGestureEvent& event) const
@@ -3084,8 +2546,7 @@ void EventHandler::setResizingFrameSet(HTMLFrameSetElement* frameSet)
 
 void EventHandler::resizeScrollableAreaDestroyed()
 {
-    ASSERT(m_resizeScrollableArea);
-    m_resizeScrollableArea = nullptr;
+    m_scrollManager.clearResizeScrollableArea(true);
 }
 
 void EventHandler::hoverTimerFired(Timer<EventHandler>*)
@@ -3155,10 +2616,10 @@ WebInputEventResult EventHandler::keyEvent(const PlatformKeyboardEvent& initialK
         capsLockStateMayHaveChanged();
 
 #if OS(WIN)
-    if (panScrollInProgress()) {
+    if (m_scrollManager.panScrollInProgress()) {
         // If a key is pressed while the panScroll is in progress then we want to stop
         if (initialKeyEvent.type() == PlatformEvent::KeyDown || initialKeyEvent.type() == PlatformEvent::RawKeyDown)
-            stopAutoscroll();
+            m_scrollManager.stopAutoscroll();
 
         // If we were in panscroll mode, we swallow the key event
         return WebInputEventResult::HandledSuppressed;
@@ -3485,7 +2946,7 @@ void EventHandler::defaultSpaceEventHandler(KeyboardEvent* event)
     ScrollDirection direction = event->shiftKey() ? ScrollBlockDirectionBackward : ScrollBlockDirectionForward;
 
     // FIXME: enable scroll customization in this case. See crbug.com/410974.
-    if (logicalScroll(direction, ScrollByPage)) {
+    if (m_scrollManager.logicalScroll(direction, ScrollByPage, nullptr, m_mousePressNode)) {
         event->setDefaultHandled();
         return;
     }
@@ -3581,12 +3042,6 @@ void EventHandler::capsLockStateMayHaveChanged()
     }
 }
 
-void EventHandler::setFrameWasScrolledByUser()
-{
-    if (DocumentLoader* documentLoader = m_frame->loader().documentLoader())
-        documentLoader->initialScrollState().wasScrolledByUser = true;
-}
-
 bool EventHandler::passMousePressEventToScrollbar(MouseEventWithHitTestResults& mev)
 {
     Scrollbar* scrollbar = mev.scrollbar();
@@ -3594,7 +3049,7 @@ bool EventHandler::passMousePressEventToScrollbar(MouseEventWithHitTestResults&
 
     if (!scrollbar || !scrollbar->enabled())
         return false;
-    setFrameWasScrolledByUser();
+    m_scrollManager.setFrameWasScrolledByUser();
     scrollbar->mouseDown(mev.event());
     return true;
 }