Refactor |LocalFrame::PositionForPoint|

This patch reduces calls to |LayoutObject::PositionForPoint|
in |LocalFrame::PositionForPoint|.

Unlike r827152 <crrev.com/c/2535530>, this one cannot
eliminate the use in all cases. Also the logic looks very
similar but has slightly differently written, there may be
some behavior changes.

Bug: 829028
Change-Id: Ife1dd69e7a24462b0370766e4cf89fb76d2de97a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2535890
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827165}

third_party/blink/renderer/core/frame/local_frame.cc

@@ -1365,19 +1365,7 @@ PositionWithAffinity LocalFrame::PositionForPoint(
     const PhysicalOffset& frame_point) {
   HitTestLocation location(frame_point);
   HitTestResult result = GetEventHandler().HitTestResultAtLocation(location);
-  Node* node = result.InnerPossiblyPseudoNode();
-  if (node && !node->IsPseudoElement())
-    node = result.InnerNodeOrImageMapImage();
-  if (!node)
-    return PositionWithAffinity();
-  LayoutObject* layout_object = node->GetLayoutObject();
-  if (!layout_object)
-    return PositionWithAffinity();
-  const PositionWithAffinity position =
-      layout_object->PositionForPoint(result.LocalPoint());
-  if (position.IsNull())
-    return PositionWithAffinity(FirstPositionInOrBeforeNode(*node));
-  return position;
+  return result.GetPositionForInnerNodeOrImageMapImage();
 }
 
 Document* LocalFrame::DocumentAtPoint(

third_party/blink/renderer/core/layout/hit_test_result.cc

@@ -173,6 +173,27 @@ PositionWithAffinity HitTestResult::GetPosition() const {
   return layout_object->PositionForPoint(LocalPoint());
 }
 
+PositionWithAffinity HitTestResult::GetPositionForInnerNodeOrImageMapImage()
+    const {
+  Node* node = InnerPossiblyPseudoNode();
+  if (node && !node->IsPseudoElement())
+    node = InnerNodeOrImageMapImage();
+  if (!node)
+    return PositionWithAffinity();
+  LayoutObject* layout_object = node->GetLayoutObject();
+  if (!layout_object)
+    return PositionWithAffinity();
+  PositionWithAffinity position;
+  if (box_fragment_ && NGPhysicalBoxFragment::SupportsPositionForPoint() &&
+      layout_object == GetLayoutObject())
+    position = box_fragment_->PositionForPoint(LocalPoint());
+  else
+    position = layout_object->PositionForPoint(LocalPoint());
+  if (position.IsNull())
+    return PositionWithAffinity(FirstPositionInOrBeforeNode(*node));
+  return position;
+}
+
 LayoutObject* HitTestResult::GetLayoutObject() const {
   return inner_node_ ? inner_node_->GetLayoutObject() : nullptr;
 }

third_party/blink/renderer/core/layout/hit_test_result.h

@@ -134,6 +134,7 @@ class CORE_EXPORT HitTestResult {
   }
 
   PositionWithAffinity GetPosition() const;
+  PositionWithAffinity GetPositionForInnerNodeOrImageMapImage() const;
   LayoutObject* GetLayoutObject() const;
 
   void SetToShadowHostIfInRestrictedShadowRoot();