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 815b6fd8477e27b856d2cca41cda261247a65e32..bd0a7a00b7a991ad663588c7a280442b2e048911 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/paint/PaintLayer.h"
+#include "core/svg/SVGDocumentExtensions.h"
+#include "platform/geometry/FloatQuad.h"
 
 namespace blink {
 
@@ -33,8 +54,66 @@ PlatformMouseEvent mouseEventWithRegion(Node* node,
   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::MouseEventManager(LocalFrame* frame,
+                                     ScrollManager* scrollManager)
+    : m_frame(frame),
+      m_scrollManager(scrollManager),
+      m_fakeMouseMoveEventTimer(
+          this,
+          &MouseEventManager::fakeMouseMoveEventTimerFired) {
+  clear();
+}
+
+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);
+}
+
 MouseEventManager::MouseEventBoundaryEventDispatcher::
     MouseEventBoundaryEventDispatcher(
         MouseEventManager* mouseEventManager,
@@ -95,7 +174,7 @@ void MouseEventManager::MouseEventBoundaryEventDispatcher::dispatch(
     const PlatformMouseEvent& platformMouseEvent,
     bool checkForListener) {
   m_mouseEventManager->dispatchMouseEvent(target, type, platformMouseEvent,
-                                          relatedTarget, 0, checkForListener);
+                                          relatedTarget, checkForListener);
 }
 
 void MouseEventManager::sendBoundaryEvents(
@@ -112,29 +191,817 @@ 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,
-        relatedTarget ? relatedTarget->toNode() : nullptr);
+        mouseEventType, targetNode->document().domWindow(), mouseEvent,
+        clickCount, relatedTarget ? relatedTarget->toNode() : nullptr);
     DispatchEventResult dispatchResult = target->dispatchEvent(event);
     return EventHandlingUtil::toWebInputEventResult(dispatchResult);
   }
   return WebInputEventResult::NotHandled;
 }
 
-MouseEventManager::MouseEventManager(LocalFrame* frame) : m_frame(frame) {
-  clear();
+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);
 }
 
-void MouseEventManager::clear() {}
+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
 
-DEFINE_TRACE(MouseEventManager) {
-  visitor->trace(m_frame);
-  visitor->trace(m_nodeUnderMouse);
+  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;
 }
 
 }  // namespace blink