Add a flag to update hover effect when a layout is changed

third_party/WebKit/Source/core/frame/LocalFrameView.cpp

Index: third_party/WebKit/Source/core/frame/LocalFrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/LocalFrameView.cpp b/third_party/WebKit/Source/core/frame/LocalFrameView.cpp
index f0a5ea25c309b9158561feab00cf5ea3fa2063c5..64e34aef7523db8c34c39b7a1495f0559a2556c1 100644
--- a/third_party/WebKit/Source/core/frame/LocalFrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/LocalFrameView.cpp
@@ -2597,7 +2597,15 @@ void LocalFrameView::PerformPostLayoutTasks() {
   // if there are no RemoteFrame ancestors in the frame tree. Use of
   // localFrameRoot() is discouraged but will change when cursor update
   // scheduling is moved from EventHandler to PageEventHandler.
-  GetFrame().LocalFrameRoot().GetEventHandler().ScheduleCursorUpdate();
+
+  // Fire a fake a mouse move event to update hover state and mouse cursor, and
+  // send the right mouse out/over events.
+  if (RuntimeEnabledFeatures::UpdateHoverPostLayoutEnabled()) {

[Navid Zolghadr, 2017/07/05 17:37:33]

If we are dragging a draggable object on the page and the page modifies the
layout say in drag event handler doesn't this cause mouse events being fired?
Then I guess we are contradicting the drag spec as it says we should not send
any input device events to the page. I believe when there is a drag operation
going on we do not update the hover states either (also it was mentioned in your
doc if I recall).

[lanwei, 2017/07/06 03:04:34]

I tested that when we are starting the drag mode, this function does not get
called. I think we won't send any mouse events.

+    frame_->GetEventHandler().DispatchFakeMouseMoveEventSoon(
+        MouseEventManager::FakeMouseMoveReason::kPerFrame);
+  } else {
+    GetFrame().LocalFrameRoot().GetEventHandler().ScheduleCursorUpdate();
+  }
 
   UpdateGeometries();
 
@@ -4168,7 +4176,8 @@ void LocalFrameView::UpdateScrollOffset(const ScrollOffset& offset,
   Document* document = frame_->GetDocument();
   document->EnqueueScrollEventForNode(document);
 
-  frame_->GetEventHandler().DispatchFakeMouseMoveEventSoon();
+  frame_->GetEventHandler().DispatchFakeMouseMoveEventSoon(
+      MouseEventManager::FakeMouseMoveReason::kDuringScroll);
   if (scroll_type == kUserScroll || scroll_type == kCompositorScroll) {
     Page* page = GetFrame().GetPage();
     if (page)