Extract more of the mouse logic from EventHandler

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

Index: third_party/WebKit/Source/core/input/MouseEventManager.cpp
diff --git a/third_party/WebKit/Source/core/input/MouseEventManager.cpp b/third_party/WebKit/Source/core/input/MouseEventManager.cpp
index 20929e3412e9aee8200f4672de952deaea4df703..7b7cf120c3c5183acb9da34cf64b8ad3515ecdd0 100644
--- a/third_party/WebKit/Source/core/input/MouseEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/MouseEventManager.cpp
@@ -4,10 +4,31 @@
 
 #include "core/input/MouseEventManager.h"
 
+#include "core/clipboard/DataObject.h"
+#include "core/clipboard/DataTransfer.h"
+#include "core/dom/Element.h"
 #include "core/dom/ElementTraversal.h"
+#include "core/editing/FrameSelection.h"
+#include "core/editing/SelectionController.h"
+#include "core/events/DragEvent.h"
 #include "core/events/MouseEvent.h"
+#include "core/frame/FrameView.h"
+#include "core/frame/LocalFrame.h"
+#include "core/frame/Settings.h"
 #include "core/html/HTMLCanvasElement.h"
+#include "core/input/EventHandler.h"
 #include "core/input/EventHandlingUtil.h"
+#include "core/input/InputDeviceCapabilities.h"
+#include "core/input/KeyboardEventManager.h"
+#include "core/layout/HitTestResult.h"
+#include "core/layout/api/LayoutViewItem.h"
+#include "core/page/AutoscrollController.h"
+#include "core/page/DragController.h"
+#include "core/page/DragState.h"
+#include "core/page/FocusController.h"
+#include "core/svg/SVGDocumentExtensions.h"
+#include "platform/geometry/FloatQuad.h"
+
 
 namespace blink {
 
@@ -32,8 +53,28 @@ PlatformMouseEvent mouseEventWithRegion(Node* node, const PlatformMouseEvent& mo
     return newMouseEvent;
 }
 
+// The amount of time to wait before sending a fake mouse event triggered
+// during a scroll.
+const double kFakeMouseMoveInterval = 0.1;
+
+#if OS(MACOSX)
+const double kTextDragDelay = 0.15;
+#else
+const double kTextDragDelay = 0.0;
+#endif
+
+// The link drag hysteresis is much larger than the others because there
+// needs to be enough space to cancel the link press without starting a link drag,
+// and because dragging links is rare.
+const int kLinkDragHysteresis = 40;
+const int kImageDragHysteresis = 5;
+const int kTextDragHysteresis = 3;
+const int kGeneralDragHysteresis = 3;
+
 } // namespace
 
+enum class DragInitiator { Mouse, Touch };
+
 MouseEventManager::MouseEventBoundaryEventDispatcher::MouseEventBoundaryEventDispatcher(
     MouseEventManager* mouseEventManager,
     const PlatformMouseEvent* platformMouseEvent,
@@ -83,7 +124,7 @@ void MouseEventManager::MouseEventBoundaryEventDispatcher::dispatch(
     const PlatformMouseEvent& platformMouseEvent, bool checkForListener)
 {
     m_mouseEventManager->dispatchMouseEvent(target, type, platformMouseEvent,
-        relatedTarget, 0, checkForListener);
+        relatedTarget, checkForListener);
 }
 
 void MouseEventManager::sendBoundaryEvents(
@@ -100,14 +141,21 @@ WebInputEventResult MouseEventManager::dispatchMouseEvent(
     const AtomicString& mouseEventType,
     const PlatformMouseEvent& mouseEvent,
     EventTarget* relatedTarget,
-    int detail,
     bool checkForListener)
 {
     if (target && target->toNode()
         && (!checkForListener || target->hasEventListeners(mouseEventType))) {
         Node* targetNode = target->toNode();
+        int clickCount = 0;
+        if (mouseEventType == EventTypeNames::mouseup
+            || mouseEventType == EventTypeNames::mousedown
+            || mouseEventType == EventTypeNames::click
+            || mouseEventType == EventTypeNames::auxclick
+            || mouseEventType == EventTypeNames::dblclick) {
+            clickCount = m_clickCount;
+        }
         MouseEvent* event = MouseEvent::create(mouseEventType,
-            targetNode->document().domWindow(), mouseEvent, detail,
+            targetNode->document().domWindow(), mouseEvent, clickCount,
             relatedTarget ? relatedTarget->toNode() : nullptr);
         DispatchEventResult dispatchResult = target->dispatchEvent(event);
         return EventHandlingUtil::toWebInputEventResult(dispatchResult);
@@ -115,20 +163,769 @@ WebInputEventResult MouseEventManager::dispatchMouseEvent(
     return WebInputEventResult::NotHandled;
 }
 
-MouseEventManager::MouseEventManager(LocalFrame* frame)
+WebInputEventResult MouseEventManager::setMousePositionAndDispatchMouseEvent(
+    Node* targetNode, const AtomicString& eventType,
+    const PlatformMouseEvent& platformMouseEvent)
+{
+    // If the target node is a text node, dispatch on the parent node.
+    if (targetNode && targetNode->isTextNode())
+        targetNode = FlatTreeTraversal::parent(*targetNode);
+
+    setNodeUnderMouse(targetNode, platformMouseEvent);
+
+    return dispatchMouseEvent(m_nodeUnderMouse, eventType, platformMouseEvent,
+        nullptr);
+}
+
+
+WebInputEventResult MouseEventManager::dispatchMouseClickIfNeeded(
+    const MouseEventWithHitTestResults& mev)
+{
+    // We only prevent click event when the click may cause contextmenu to popup.
+    // However, we always send auxclick.
+    bool contextMenuEvent = !RuntimeEnabledFeatures::auxclickEnabled()
+        && mev.event().pointerProperties().button == WebPointerProperties::Button::Right;
+#if OS(MACOSX)
+    // FIXME: The Mac port achieves the same behavior by checking whether the context menu is currently open in WebPage::mouseEvent(). Consider merging the implementations.
+    if (mev.event().pointerProperties().button == WebPointerProperties::Button::Left
+        && mev.event().getModifiers() & PlatformEvent::CtrlKey)
+        contextMenuEvent = true;
+#endif
+
+    WebInputEventResult clickEventResult = WebInputEventResult::NotHandled;
+    const bool shouldDispatchClickEvent = m_clickCount > 0
+        && !contextMenuEvent
+        && mev.innerNode() && m_clickNode
+        && mev.innerNode()->canParticipateInFlatTree() && m_clickNode->canParticipateInFlatTree()
+        && !(m_frame->eventHandler().selectionController().hasExtendedSelection() && isLinkSelection(mev));
+    if (shouldDispatchClickEvent) {
+        Node* clickTargetNode = nullptr;
+        // Updates distribution because a 'mouseup' event listener can make the
+        // tree dirty at dispatchMouseEvent() invocation above.
+        // Unless distribution is updated, commonAncestor would hit ASSERT.
+        if (m_clickNode == mev.innerNode()) {
+            clickTargetNode = m_clickNode;
+            clickTargetNode->updateDistribution();
+        } else if (m_clickNode->document() == mev.innerNode()->document()) {
+            m_clickNode->updateDistribution();
+            mev.innerNode()->updateDistribution();
+            clickTargetNode = mev.innerNode()->commonAncestor(
+                *m_clickNode, EventHandlingUtil::parentForClickEvent);
+        }
+        if (clickTargetNode) {
+            clickEventResult = dispatchMouseEvent(clickTargetNode,
+                !RuntimeEnabledFeatures::auxclickEnabled()
+                || (mev.event().pointerProperties().button == WebPointerProperties::Button::Left)
+                    ? EventTypeNames::click
+                    : EventTypeNames::auxclick, mev.event(), nullptr);
+        }
+    }
+    return clickEventResult;
+}
+
+
+void MouseEventManager::fakeMouseMoveEventTimerFired(TimerBase* timer)
+{
+    TRACE_EVENT0("input", "MouseEventManager::fakeMouseMoveEventTimerFired");
+    DCHECK(timer == &m_fakeMouseMoveEventTimer);
+    DCHECK(!m_mousePressed);
+
+    Settings* settings = m_frame->settings();
+    if (settings && !settings->deviceSupportsMouse())
+        return;
+
+    FrameView* view = m_frame->view();
+    if (!view)
+        return;
+
+    if (!m_frame->page() || !m_frame->page()->focusController().isActive())
+        return;
+
+    // Don't dispatch a synthetic mouse move event if the mouse cursor is not visible to the user.
+    if (!m_frame->page()->isCursorVisible())
+        return;
+
+    PlatformMouseEvent fakeMouseMoveEvent(m_lastKnownMousePosition, m_lastKnownMouseGlobalPosition, WebPointerProperties::Button::NoButton, PlatformEvent::MouseMoved, 0, static_cast<PlatformEvent::Modifiers>(KeyboardEventManager::getCurrentModifierState()), PlatformMouseEvent::RealOrIndistinguishable, monotonicallyIncreasingTime(), WebPointerProperties::PointerType::Mouse);
+    m_frame->eventHandler().handleMouseMoveEvent(fakeMouseMoveEvent);
+}
+
+void MouseEventManager::cancelFakeMouseMoveEvent()
+{
+    m_fakeMouseMoveEventTimer.stop();
+}
+
+void MouseEventManager::setNodeUnderMouse(
+    Node* target, const PlatformMouseEvent &platformMouseEvent)
+{
+    Node* lastNodeUnderMouse = m_nodeUnderMouse;
+    m_nodeUnderMouse = target;
+
+    PaintLayer* layerForLastNode = EventHandlingUtil::layerForNode(lastNodeUnderMouse);
+    PaintLayer* layerForNodeUnderMouse = EventHandlingUtil::layerForNode(m_nodeUnderMouse.get());
+    Page* page = m_frame->page();
+
+    if (lastNodeUnderMouse && (!m_nodeUnderMouse || m_nodeUnderMouse->document() != m_frame->document())) {
+        // The mouse has moved between frames.
+        if (LocalFrame* frame = lastNodeUnderMouse->document().frame()) {
+            if (FrameView* frameView = frame->view())
+                frameView->mouseExitedContentArea();
+        }
+    } else if (page && (layerForLastNode && (!layerForNodeUnderMouse || layerForNodeUnderMouse != layerForLastNode))) {
+        // The mouse has moved between layers.
+        if (ScrollableArea* scrollableAreaForLastNode = EventHandlingUtil::associatedScrollableArea(layerForLastNode))
+            scrollableAreaForLastNode->mouseExitedContentArea();
+    }
+
+    if (m_nodeUnderMouse && (!lastNodeUnderMouse || lastNodeUnderMouse->document() != m_frame->document())) {
+        // The mouse has moved between frames.
+        if (LocalFrame* frame = m_nodeUnderMouse->document().frame()) {
+            if (FrameView* frameView = frame->view())
+                frameView->mouseEnteredContentArea();
+        }
+    } else if (page && (layerForNodeUnderMouse && (!layerForLastNode || layerForNodeUnderMouse != layerForLastNode))) {
+        // The mouse has moved between layers.
+        if (ScrollableArea* scrollableAreaForNodeUnderMouse = EventHandlingUtil::associatedScrollableArea(layerForNodeUnderMouse))
+            scrollableAreaForNodeUnderMouse->mouseEnteredContentArea();
+    }
+
+    if (lastNodeUnderMouse && lastNodeUnderMouse->document() != m_frame->document()) {
+        lastNodeUnderMouse = nullptr;
+    }
+
+    sendBoundaryEvents(lastNodeUnderMouse, m_nodeUnderMouse, platformMouseEvent);
+}
+
+void MouseEventManager::nodeWillBeRemoved(Node& nodeToBeRemoved)
+{
+    if (nodeToBeRemoved.isShadowIncludingInclusiveAncestorOf(m_clickNode.get())) {
+        // We don't dispatch click events if the mousedown node is removed
+        // before a mouseup event. It is compatible with IE and Firefox.
+        m_clickNode = nullptr;
+    }
+}
+
+Node* MouseEventManager::getNodeUnderMouse()
+{
+    return m_nodeUnderMouse;
+}
+
+WebInputEventResult MouseEventManager::handleMouseFocus(const HitTestResult& hitTestResult, InputDeviceCapabilities* sourceCapabilities)
+{
+    // If clicking on a frame scrollbar, do not mess up with content focus.
+    if (hitTestResult.scrollbar() && !m_frame->contentLayoutItem().isNull()) {
+        if (hitTestResult.scrollbar()->getScrollableArea() == m_frame->contentLayoutItem().getScrollableArea())
+            return WebInputEventResult::NotHandled;
+    }
+
+    // The layout needs to be up to date to determine if an element is focusable.
+    m_frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();
+
+    Element* element = nullptr;
+    if (m_nodeUnderMouse)
+        element = m_nodeUnderMouse->isElementNode() ? toElement(m_nodeUnderMouse) : m_nodeUnderMouse->parentOrShadowHostElement();
+    for (; element; element = element->parentOrShadowHostElement()) {
+        if (element->isFocusable() && element->isFocusedElementInDocument())
+            return WebInputEventResult::NotHandled;
+        if (element->isMouseFocusable())
+            break;
+    }
+    DCHECK(!element || element->isMouseFocusable());
+
+    // To fix <rdar://problem/4895428> Can't drag selected ToDo, we don't focus
+    // a node on mouse down if it's selected and inside a focused node. It will
+    // be focused if the user does a mouseup over it, however, because the
+    // mouseup will set a selection inside it, which will call
+    // FrameSelection::setFocusedNodeIfNeeded.
+    if (element && m_frame->selection().isRange()) {
+        // TODO(yosin) We should not create |Range| object for calling
+        // |isNodeFullyContained()|.
+        if (createRange(m_frame->selection().selection().toNormalizedEphemeralRange())->isNodeFullyContained(*element)
+            && element->isDescendantOf(m_frame->document()->focusedElement()))
+            return WebInputEventResult::NotHandled;
+    }
+
+
+    // Only change the focus when clicking scrollbars if it can transfered to a
+    // mouse focusable node.
+    if (!element && hitTestResult.scrollbar())
+        return WebInputEventResult::HandledSystem;
+
+    if (Page* page = m_frame->page()) {
+        // If focus shift is blocked, we eat the event. Note we should never
+        // clear swallowEvent if the page already set it (e.g., by canceling
+        // default behavior).
+        if (element) {
+            if (slideFocusOnShadowHostIfNecessary(*element))
+                return WebInputEventResult::HandledSystem;
+            if (!page->focusController().setFocusedElement(element, m_frame, FocusParams(SelectionBehaviorOnFocus::None, WebFocusTypeMouse, sourceCapabilities)))
+                return WebInputEventResult::HandledSystem;
+        } else {
+            // We call setFocusedElement even with !element in order to blur
+            // current focus element when a link is clicked; this is expected by
+            // some sites that rely on onChange handlers running from form
+            // fields before the button click is processed.
+            if (!page->focusController().setFocusedElement(nullptr, m_frame, FocusParams(SelectionBehaviorOnFocus::None, WebFocusTypeNone, sourceCapabilities)))
+                return WebInputEventResult::HandledSystem;
+        }
+    }
+
+    return WebInputEventResult::NotHandled;
+}
+
+bool MouseEventManager::slideFocusOnShadowHostIfNecessary(const Element& element)
+{
+    if (element.authorShadowRoot() && element.authorShadowRoot()->delegatesFocus()) {
+        Document* doc = m_frame->document();
+        if (element.isShadowIncludingInclusiveAncestorOf(doc->focusedElement())) {
+            // If the inner element is already focused, do nothing.
+            return true;
+        }
+
+        // If the host has a focusable inner element, focus it. Otherwise, the host takes focus.
+        Page* page = m_frame->page();
+        DCHECK(page);
+        Element* found = page->focusController().findFocusableElementInShadowHost(element);
+        if (found && element.isShadowIncludingInclusiveAncestorOf(found)) {
+            // Use WebFocusTypeForward instead of WebFocusTypeMouse here to mean the focus has slided.
+            found->focus(FocusParams(SelectionBehaviorOnFocus::Reset, WebFocusTypeForward, nullptr));
+            return true;
+        }
+    }
+    return false;
+}
+
+void MouseEventManager::handleMousePressEventUpdateStates(
+    const PlatformMouseEvent& mouseEvent) {
+    cancelFakeMouseMoveEvent();
+    m_mousePressed = true;
+    m_capturesDragging = true;
+    setLastKnownMousePosition(mouseEvent);
+    m_mouseDownMayStartDrag = false;
+    m_mouseDownMayStartAutoscroll = false;
+    m_mouseDownTimestamp = mouseEvent.timestamp();
+
+    if (FrameView* view = m_frame->view()) {
+        m_mouseDownPos = view->rootFrameToContents(mouseEvent.position());
+    } else {
+        invalidateClick();
+    }
+}
+
+bool MouseEventManager::isMousePositionUnknown()
+{
+    return m_isMousePositionUnknown;
+}
+
+IntPoint MouseEventManager::lastKnownMousePosition()
+{
+    return m_lastKnownMousePosition;
+}
+
+void MouseEventManager::setLastKnownMousePosition(const PlatformMouseEvent& event)
+{
+    m_isMousePositionUnknown = false;
+    m_lastKnownMousePosition = event.position();
+    m_lastKnownMouseGlobalPosition = event.globalPosition();
+}
+
+void MouseEventManager::dispatchFakeMouseMoveEventSoon()
+{
+    if (m_mousePressed)
+        return;
+
+    if (m_isMousePositionUnknown)
+        return;
+
+    Settings* settings = m_frame->settings();
+    if (settings && !settings->deviceSupportsMouse())
+        return;
+
+    // Reschedule the timer, to prevent dispatching mouse move events
+    // during a scroll. This avoids a potential source of scroll jank.
+    if (m_fakeMouseMoveEventTimer.isActive())
+        m_fakeMouseMoveEventTimer.stop();
+    m_fakeMouseMoveEventTimer.startOneShot(kFakeMouseMoveInterval, BLINK_FROM_HERE);
+}
+
+void MouseEventManager::dispatchFakeMouseMoveEventSoonInQuad(const FloatQuad& quad)
+{
+    FrameView* view = m_frame->view();
+    if (!view)
+        return;
+
+    if (!quad.containsPoint(view->rootFrameToContents(m_lastKnownMousePosition)))
+        return;
+
+    dispatchFakeMouseMoveEventSoon();
+}
+
+WebInputEventResult MouseEventManager::handleMousePressEvent(const MouseEventWithHitTestResults& event)
+{
+    TRACE_EVENT0("blink", "MouseEventManager::handleMousePressEvent");
+
+    // Reset drag state.
+    dragState().m_dragSrc = nullptr;
+
+    cancelFakeMouseMoveEvent();
+
+    m_frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();
+
+    if (FrameView* frameView = m_frame->view()) {
+        if (frameView->isPointInScrollbarCorner(event.event().position()))
+            return WebInputEventResult::NotHandled;
+    }
+
+    bool singleClick = event.event().clickCount() <= 1;
+
+    m_mouseDownMayStartDrag = singleClick && !isLinkSelection(event) && !isExtendingSelection(event);
+
+    m_frame->eventHandler().selectionController().handleMousePressEvent(event);
+
+    m_mouseDown = event.event();
+
+    if (m_frame->document()->isSVGDocument() && m_frame->document()->accessSVGExtensions().zoomAndPanEnabled()) {
+        if (event.event().shiftKey() && singleClick) {
+            m_svgPan = true;
+            m_frame->document()->accessSVGExtensions().startPan(m_frame->view()->rootFrameToContents(event.event().position()));
+            return WebInputEventResult::HandledSystem;
+        }
+    }
+
+    // We don't do this at the start of mouse down handling,
+    // because we don't want to do it until we know we didn't hit a widget.
+    if (singleClick)
+        focusDocumentView();
+
+    Node* innerNode = event.innerNode();
+
+    m_mousePressNode = innerNode;
+    m_frame->document()->setSequentialFocusNavigationStartingPoint(innerNode);
+    m_dragStartPos = event.event().position();
+
+    bool swallowEvent = false;
+    m_mousePressed = true;
+
+    if (event.event().clickCount() == 2)
+        swallowEvent = m_frame->eventHandler().selectionController().handleMousePressEventDoubleClick(event);
+    else if (event.event().clickCount() >= 3)
+        swallowEvent = m_frame->eventHandler().selectionController().handleMousePressEventTripleClick(event);
+    else
+        swallowEvent = m_frame->eventHandler().selectionController().handleMousePressEventSingleClick(event);
+
+    m_mouseDownMayStartAutoscroll = m_frame->eventHandler().selectionController().mouseDownMayStartSelect()
+        || (m_mousePressNode && m_mousePressNode->layoutBox() && m_mousePressNode->layoutBox()->canBeProgramaticallyScrolled());
+
+    return swallowEvent ? WebInputEventResult::HandledSystem : WebInputEventResult::NotHandled;
+}
+
+WebInputEventResult MouseEventManager::handleMouseReleaseEvent(const MouseEventWithHitTestResults& event)
+{
+    AutoscrollController* controller = m_scrollManager->autoscrollController();
+    if (controller && controller->autoscrollInProgress())
+        m_scrollManager->stopAutoscroll();
+
+    return m_frame->eventHandler().selectionController().handleMouseReleaseEvent(event, m_dragStartPos) ? WebInputEventResult::HandledSystem : WebInputEventResult::NotHandled;
+}
+
+void MouseEventManager::updateSelectionForMouseDrag()
+{
+    m_frame->eventHandler().selectionController().updateSelectionForMouseDrag(m_mousePressNode, m_dragStartPos, m_lastKnownMousePosition);
+}
+
+bool MouseEventManager::handleDragDropIfPossible(const GestureEventWithHitTestResults& targetedEvent)
+{
+    if (m_frame->settings() && m_frame->settings()->touchDragDropEnabled() && m_frame->view()) {
+        const PlatformGestureEvent& gestureEvent = targetedEvent.event();
+        IntPoint adjustedPoint = gestureEvent.position();
+        unsigned modifiers = gestureEvent.getModifiers();
+
+        // TODO(mustaq): Suppressing long-tap MouseEvents could break
+        // drag-drop. Will do separately because of the risk. crbug.com/606938.
+        PlatformMouseEvent mouseDownEvent(adjustedPoint, gestureEvent.globalPosition(), WebPointerProperties::Button::Left, PlatformEvent::MousePressed, 1,
+            static_cast<PlatformEvent::Modifiers>(modifiers | PlatformEvent::LeftButtonDown),
+            PlatformMouseEvent::FromTouch, WTF::monotonicallyIncreasingTime(), WebPointerProperties::PointerType::Mouse);
+        m_mouseDown = mouseDownEvent;
+
+        PlatformMouseEvent mouseDragEvent(adjustedPoint, gestureEvent.globalPosition(), WebPointerProperties::Button::Left, PlatformEvent::MouseMoved, 1,
+            static_cast<PlatformEvent::Modifiers>(modifiers | PlatformEvent::LeftButtonDown),
+            PlatformMouseEvent::FromTouch, WTF::monotonicallyIncreasingTime(), WebPointerProperties::PointerType::Mouse);
+        HitTestRequest request(HitTestRequest::ReadOnly);
+        MouseEventWithHitTestResults mev = EventHandlingUtil::performMouseEventHitTest(m_frame, request, mouseDragEvent);
+        m_mouseDownMayStartDrag = true;
+        dragState().m_dragSrc = nullptr;
+        m_mouseDownPos = m_frame->view()->rootFrameToContents(mouseDragEvent.position());
+        return handleDrag(mev, DragInitiator::Touch);
+    }
+    return false;
+}
+
+void MouseEventManager::focusDocumentView()
+{
+    Page* page = m_frame->page();
+    if (!page)
+        return;
+    page->focusController().focusDocumentView(m_frame);
+}
+
+WebInputEventResult MouseEventManager::handleMouseDraggedEvent(const MouseEventWithHitTestResults& event)
+{
+    TRACE_EVENT0("blink", "MouseEventManager::handleMouseDraggedEvent");
+
+    // While resetting m_mousePressed here may seem out of place, it turns out
+    // to be needed to handle some bugs^Wfeatures in Blink mouse event handling:
+    // 1. Certain elements, such as <embed>, capture mouse events. They do not
+    //    bubble back up. One way for a <embed> to start capturing mouse events
+    //    is on a mouse press. The problem is the <embed> node only starts
+    //    capturing mouse events *after* m_mousePressed for the containing frame
+    //    has already been set to true. As a result, the frame's EventHandler
+    //    never sees the mouse release event, which is supposed to reset
+    //    m_mousePressed... so m_mousePressed ends up remaining true until the
+    //    event handler finally gets another mouse released event. Oops.
+    // 2. Dragging doesn't start until after a mouse press event, but a drag
+    //    that ends as a result of a mouse release does not send a mouse release
+    //    event. As a result, m_mousePressed also ends up remaining true until
+    //    the next mouse release event seen by the EventHandler.
+    if (event.event().pointerProperties().button != WebPointerProperties::Button::Left)
+        m_mousePressed = false;
+
+    if (!m_mousePressed)
+        return WebInputEventResult::NotHandled;
+
+    if (handleDrag(event, DragInitiator::Mouse))
+        return WebInputEventResult::HandledSystem;
+
+    Node* targetNode = event.innerNode();
+    if (!targetNode)
+        return WebInputEventResult::NotHandled;
+
+    LayoutObject* layoutObject = targetNode->layoutObject();
+    if (!layoutObject) {
+        Node* parent = FlatTreeTraversal::parent(*targetNode);
+        if (!parent)
+            return WebInputEventResult::NotHandled;
+
+        layoutObject = parent->layoutObject();
+        if (!layoutObject || !layoutObject->isListBox())
+            return WebInputEventResult::NotHandled;
+    }
+
+    m_mouseDownMayStartDrag = false;
+
+    if (m_mouseDownMayStartAutoscroll && !m_scrollManager->middleClickAutoscrollInProgress()) {
+        if (AutoscrollController* controller = m_scrollManager->autoscrollController()) {
+            controller->startAutoscrollForSelection(layoutObject);
+            m_mouseDownMayStartAutoscroll = false;
+        }
+    }
+
+    m_frame->eventHandler().selectionController().handleMouseDraggedEvent(event, m_mouseDownPos, m_dragStartPos, m_mousePressNode.get(), m_lastKnownMousePosition);
+    return WebInputEventResult::HandledSystem;
+}
+
+
+bool MouseEventManager::handleDrag(const MouseEventWithHitTestResults& event, DragInitiator initiator)
+{
+    DCHECK(event.event().type() == PlatformEvent::MouseMoved);
+    // Callers must protect the reference to FrameView, since this function may dispatch DOM
+    // events, causing page/FrameView to go away.
+    DCHECK(m_frame);
+    DCHECK(m_frame->view());
+    if (!m_frame->page())
+        return false;
+
+    if (m_mouseDownMayStartDrag) {
+        HitTestRequest request(HitTestRequest::ReadOnly);
+        HitTestResult result(request, m_mouseDownPos);
+        m_frame->contentLayoutItem().hitTest(result);
+        Node* node = result.innerNode();
+        if (node) {
+            DragController::SelectionDragPolicy selectionDragPolicy = event.event().timestamp() - m_mouseDownTimestamp < kTextDragDelay
+                ? DragController::DelayedSelectionDragResolution
+                : DragController::ImmediateSelectionDragResolution;
+            dragState().m_dragSrc = m_frame->page()->dragController().draggableNode(m_frame, node, m_mouseDownPos, selectionDragPolicy, dragState().m_dragType);
+        } else {
+            dragState().m_dragSrc = nullptr;
+        }
+
+        if (!dragState().m_dragSrc)
+            m_mouseDownMayStartDrag = false; // no element is draggable
+    }
+
+    if (!m_mouseDownMayStartDrag)
+        return initiator == DragInitiator::Mouse && !m_frame->eventHandler().selectionController().mouseDownMayStartSelect() && !m_mouseDownMayStartAutoscroll;
+
+    // We are starting a text/image/url drag, so the cursor should be an arrow
+    // FIXME <rdar://7577595>: Custom cursors aren't supported during drag and drop (default to pointer).
+    m_frame->view()->setCursor(pointerCursor());
+
+    if (initiator == DragInitiator::Mouse && !dragHysteresisExceeded(event.event().position()))
+        return true;
+
+    // Once we're past the hysteresis point, we don't want to treat this gesture as a click
+    invalidateClick();
+
+    if (!tryStartDrag(event)) {
+        // Something failed to start the drag, clean up.
+        clearDragDataTransfer();
+        dragState().m_dragSrc = nullptr;
+    }
+
+    m_mouseDownMayStartDrag = false;
+    // Whether or not the drag actually started, no more default handling (like selection).
+    return true;
+}
+
+DataTransfer* MouseEventManager::createDraggingDataTransfer() const
+{
+    return DataTransfer::create(DataTransfer::DragAndDrop, DataTransferWritable, DataObject::create());
+}
+
+bool MouseEventManager::tryStartDrag(const MouseEventWithHitTestResults& event)
+{
+    // The DataTransfer would only be non-empty if we missed a dragEnd.
+    // Clear it anyway, just to make sure it gets numbified.
+    clearDragDataTransfer();
+
+    dragState().m_dragDataTransfer = createDraggingDataTransfer();
+
+    // Check to see if this a DOM based drag, if it is get the DOM specified drag
+    // image and offset
+    if (dragState().m_dragType == DragSourceActionDHTML) {
+        if (LayoutObject* layoutObject = dragState().m_dragSrc->layoutObject()) {
+            IntRect boundingIncludingDescendants = layoutObject->absoluteBoundingBoxRectIncludingDescendants();
+            IntSize delta = m_mouseDownPos - boundingIncludingDescendants.location();
+            dragState().m_dragDataTransfer->setDragImageElement(dragState().m_dragSrc.get(), IntPoint(delta));
+        } else {
+            // The layoutObject has disappeared, this can happen if the onStartDrag handler has hidden
+            // the element in some way. In this case we just kill the drag.
+            return false;
+        }
+    }
+
+    DragController& dragController = m_frame->page()->dragController();
+    if (!dragController.populateDragDataTransfer(m_frame, dragState(), m_mouseDownPos))
+        return false;
+
+    // If dispatching dragstart brings about another mouse down -- one way
+    // this will happen is if a DevTools user breaks within a dragstart
+    // handler and then clicks on the suspended page -- the drag state is
+    // reset. Hence, need to check if this particular drag operation can
+    // continue even if dispatchEvent() indicates no (direct) cancellation.
+    // Do that by checking if m_dragSrc is still set.
+    m_mouseDownMayStartDrag = dispatchDragSrcEvent(EventTypeNames::dragstart, m_mouseDown) == WebInputEventResult::NotHandled
+        && !m_frame->selection().isInPasswordField() && dragState().m_dragSrc;
+
+    // Invalidate clipboard here against anymore pasteboard writing for security. The drag
+    // image can still be changed as we drag, but not the pasteboard data.
+    dragState().m_dragDataTransfer->setAccessPolicy(DataTransferImageWritable);
+
+    if (m_mouseDownMayStartDrag) {
+        // Dispatching the event could cause Page to go away. Make sure it's still valid before trying to use DragController.
+        if (m_frame->page() && dragController.startDrag(m_frame, dragState(), event.event(), m_mouseDownPos))
+            return true;
+        // Drag was canned at the last minute - we owe m_dragSrc a DRAGEND event
+        dispatchDragSrcEvent(EventTypeNames::dragend, event.event());
+    }
+
+    return false;
+}
+
+// returns if we should continue "default processing", i.e., whether eventhandler canceled
+WebInputEventResult MouseEventManager::dispatchDragSrcEvent(const AtomicString& eventType, const PlatformMouseEvent& event)
+{
+    return dispatchDragEvent(eventType, dragState().m_dragSrc.get(), event, dragState().m_dragDataTransfer.get());
+}
+
+WebInputEventResult MouseEventManager::dispatchDragEvent(const AtomicString& eventType, Node* dragTarget, const PlatformMouseEvent& event, DataTransfer* dataTransfer)
+{
+    FrameView* view = m_frame->view();
+
+    // FIXME: We might want to dispatch a dragleave even if the view is gone.
+    if (!view)
+        return WebInputEventResult::NotHandled;
+
+    DragEvent* me = DragEvent::create(eventType,
+        true, true, m_frame->document()->domWindow(),
+        0, event.globalPosition().x(), event.globalPosition().y(), event.position().x(), event.position().y(),
+        event.movementDelta().x(), event.movementDelta().y(),
+        event.getModifiers(),
+        0, MouseEvent::platformModifiersToButtons(event.getModifiers()), nullptr, event.timestamp(), dataTransfer, event.getSyntheticEventType());
+
+    return EventHandlingUtil::toWebInputEventResult(dragTarget->dispatchEvent(me));
+}
+
+void MouseEventManager::clearDragDataTransfer()
+{
+    if (dragState().m_dragDataTransfer) {
+        dragState().m_dragDataTransfer->clearDragImage();
+        dragState().m_dragDataTransfer->setAccessPolicy(DataTransferNumb);
+    }
+}
+
+void MouseEventManager::dragSourceEndedAt(const PlatformMouseEvent& event, DragOperation operation)
+{
+    // Send a hit test request so that Layer gets a chance to update the :hover and :active pseudoclasses.
+    HitTestRequest request(HitTestRequest::Release);
+    EventHandlingUtil::performMouseEventHitTest(m_frame, request, event);
+
+    if (dragState().m_dragSrc) {
+        dragState().m_dragDataTransfer->setDestinationOperation(operation);
+        // for now we don't care if event handler cancels default behavior, since there is none
+        dispatchDragSrcEvent(EventTypeNames::dragend, event);
+    }
+    clearDragDataTransfer();
+    dragState().m_dragSrc = nullptr;
+    // In case the drag was ended due to an escape key press we need to ensure
+    // that consecutive mousemove events don't reinitiate the drag and drop.
+    m_mouseDownMayStartDrag = false;
+}
+
+DragState& MouseEventManager::dragState()
+{
+    DEFINE_STATIC_LOCAL(DragState, state, (new DragState));
+    return state;
+}
+
+bool MouseEventManager::dragHysteresisExceeded(const IntPoint& dragLocationInRootFrame) const
+{
+    FrameView* view = m_frame->view();
+    if (!view)
+        return false;
+    IntPoint dragLocation = view->rootFrameToContents(dragLocationInRootFrame);
+    IntSize delta = dragLocation - m_mouseDownPos;
+
+    int threshold = kGeneralDragHysteresis;
+    switch (dragState().m_dragType) {
+    case DragSourceActionSelection:
+        threshold = kTextDragHysteresis;
+        break;
+    case DragSourceActionImage:
+        threshold = kImageDragHysteresis;
+        break;
+    case DragSourceActionLink:
+        threshold = kLinkDragHysteresis;
+        break;
+    case DragSourceActionDHTML:
+        break;
+    case DragSourceActionNone:
+        NOTREACHED();
+    }
+
+    return abs(delta.width()) >= threshold || abs(delta.height()) >= threshold;
+}
+
+void MouseEventManager::clearDragHeuristicState()
+{
+    // Used to prevent mouseMoveEvent from initiating a drag before
+    // the mouse is pressed again.
+    m_mousePressed = false;
+    m_capturesDragging = false;
+    m_mouseDownMayStartDrag = false;
+    m_mouseDownMayStartAutoscroll = false;
+}
+
+bool MouseEventManager::handleSvgPanIfNeeded(bool isReleaseEvent)
+{
+    if (!m_svgPan)
+        return false;
+    m_svgPan = !isReleaseEvent;
+    m_frame->document()->accessSVGExtensions().updatePan(m_frame->view()->rootFrameToContents(m_lastKnownMousePosition));
+    return true;
+}
+
+void MouseEventManager::invalidateClick()
+{
+    m_clickCount = 0;
+    m_clickNode = nullptr;
+}
+
+bool MouseEventManager::mousePressed()
+{
+    return m_mousePressed;
+}
+
+void MouseEventManager::setMousePressed(bool mousePressed)
+{
+    m_mousePressed = mousePressed;
+}
+
+bool MouseEventManager::capturesDragging() const
+{
+    return m_capturesDragging;
+}
+
+void MouseEventManager::setCapturesDragging(bool capturesDragging)
+{
+    m_capturesDragging = capturesDragging;
+}
+
+Node* MouseEventManager::mousePressNode()
+{
+    return m_mousePressNode;
+}
+
+void MouseEventManager::setMousePressNode(Node* node)
+{
+    m_mousePressNode = node;
+}
+
+void MouseEventManager::setClickNode(Node* node)
+{
+    m_clickNode = node;
+}
+
+void MouseEventManager::setClickCount(int clickCount)
+{
+    m_clickCount = clickCount;
+}
+
+bool MouseEventManager::mouseDownMayStartDrag()
+{
+    return m_mouseDownMayStartDrag;
+}
+
+MouseEventManager::MouseEventManager(LocalFrame* frame,
+    ScrollManager* scrollManager)
     : m_frame(frame)
+    , m_scrollManager(scrollManager)
+    , m_fakeMouseMoveEventTimer(this, &MouseEventManager::fakeMouseMoveEventTimerFired)
 {
     clear();
 }
 
+MouseEventManager::~MouseEventManager()

[bokan, 2016/09/30 16:57:55]

For consistency with other code, we usually have the constructor, destructor,
trace and those kinds of methods near the top.

[Navid Zolghadr, 2016/10/03 16:03:01]

Done.

+{
+    DCHECK(!m_fakeMouseMoveEventTimer.isActive());

[bokan, 2016/09/30 16:57:55]

Do we really need this check? It's the only reason we need to finalize this
class...

[Navid Zolghadr, 2016/10/03 16:03:01]

Probably not. I just tried to keep that. But Let's just get rid of it :)

+}
+
 void MouseEventManager::clear()
 {
+    m_nodeUnderMouse = nullptr;
+    m_mousePressNode = nullptr;
+    m_mouseDownMayStartAutoscroll = false;
+    m_mouseDownMayStartDrag = false;
+    m_capturesDragging = false;
+    m_isMousePositionUnknown = true;
+    m_lastKnownMousePosition = IntPoint();
+    m_lastKnownMouseGlobalPosition = IntPoint();
+    m_mousePressed = false;
+    m_clickCount = 0;
+    m_clickNode = nullptr;
+    m_mouseDownPos = IntPoint();
+    m_mouseDownTimestamp = 0;
+    m_mouseDown = PlatformMouseEvent();
+    m_svgPan = false;
+    m_dragStartPos = LayoutPoint();
+    m_fakeMouseMoveEventTimer.stop();
 }
 
 DEFINE_TRACE(MouseEventManager)
 {
     visitor->trace(m_frame);
+    visitor->trace(m_scrollManager);
     visitor->trace(m_nodeUnderMouse);
+    visitor->trace(m_mousePressNode);
+    visitor->trace(m_clickNode);
 }
 
 } // namespace blink