Fix hit-testing for scrolling content

This patch changes |SelectionControllerTest| to use the
unified |HitTestResult::GetPosition()| added in r827165
<crrev.com/c/2535890>. This makes the tests to run the same
code when |LayoutNGFullPositionForPoint| is enabled.

By switching to the unified code, the test for
crbug.com/985779 started to fail, because when inner node is
inline, |LocalPoint()| is in the content coordinate system,
not in the container coordinate system, that
|PositionForPoint| should not add |ScrolledContentOffset|.
Before |LayoutNGFullPositionForPoint| is enabled, this was
done in |LayoutObject| virtual functions.

Bug: 985779, 1150362, 829028
Change-Id: Ie16d228679778e64170720da105ba47bc6c3557f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2567059Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832337}

third_party/blink/renderer/core/editing/selection_controller_test.cc

@@ -35,8 +35,7 @@ class SelectionControllerTest : public EditingTestBase {
 
   static PositionWithAffinity GetPositionFromHitTestResult(
       const HitTestResult& hit_test_result) {
-    return hit_test_result.InnerNode()->GetLayoutObject()->PositionForPoint(
-        hit_test_result.LocalPoint());
+    return hit_test_result.GetPosition();
   }
 
   PositionWithAffinity GetPositionAtLocation(const IntPoint& point) {

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

@@ -186,8 +186,13 @@ PositionWithAffinity HitTestResult::GetPosition() const {
   // relayout?
   if (box_fragment_ &&
       RuntimeEnabledFeatures::LayoutNGFullPositionForPointEnabled() &&
-      !box_fragment_->IsLayoutObjectDestroyedOrMoved())
-    return box_fragment_->PostLayout()->PositionForPoint(LocalPoint());
+      !box_fragment_->IsLayoutObjectDestroyedOrMoved()) {
+    const NGPhysicalBoxFragment* fragment = box_fragment_->PostLayout();
+    // When the node is an inline object, |fragment| is the container fragment,
+    // and |LocalPoint()| is relative to the content.
+    const bool is_content_offset = fragment->GetLayoutObject() != layout_object;
+    return fragment->PositionForPoint(LocalPoint(), is_content_offset);
+  }
   return layout_object->PositionForPoint(LocalPoint());
 }
 

third_party/blink/renderer/core/layout/ng/ng_physical_box_fragment.cc

@@ -802,7 +802,8 @@ void NGPhysicalBoxFragment::AddOutlineRectsForInlineBox(
 }
 
 PositionWithAffinity NGPhysicalBoxFragment::PositionForPoint(
-    PhysicalOffset point) const {
+    PhysicalOffset point,
+    bool is_content_offset) const {
   if (layout_object_->IsBox() && !layout_object_->IsLayoutNGObject()) {
     // Layout engine boundary. Enter legacy PositionForPoint().
     return layout_object_->PositionForPoint(point);
@@ -816,7 +817,7 @@ PositionWithAffinity NGPhysicalBoxFragment::PositionForPoint(
   DCHECK(!IsAtomicInline() ||
          PhysicalRect(PhysicalOffset(), Size()).Contains(point));
 
-  if (IsScrollContainer())
+  if (!is_content_offset && IsScrollContainer())
     point += PhysicalOffset(PixelSnappedScrolledContentOffset());
 
   if (const NGFragmentItems* items = Items()) {

third_party/blink/renderer/core/layout/ng/ng_physical_box_fragment.h

@@ -246,7 +246,10 @@ class CORE_EXPORT NGPhysicalBoxFragment final
                        NGOutlineType include_block_overflows,
                        Vector<PhysicalRect>* outline_rects) const;
 
-  PositionWithAffinity PositionForPoint(PhysicalOffset) const;
+  // When |is_content_offset|, the offset is relative to the content, not to the
+  // scroll container.
+  PositionWithAffinity PositionForPoint(PhysicalOffset,
+                                        bool is_content_offset = false) const;
 
   UBiDiLevel BidiLevel() const;