Snav: Remove the redundant CanBeScrolledIntoView()

This simplifies spatnav's inner loop, the evaluation of
DOM nodes when looking for candidates, a tiny bit.

Now that CanBeScrolledIntoView lost its call site
we can remove it completely to reduce spatnav's
code footprint.

Bug: 770147
Test: snav-div-overflow-scroll-hidden.html
Change-Id: Icbf4cb4d0274d63658dbeab1cdae1ce63557576f
Reviewed-on: https://chromium-review.googlesource.com/c/1319678
Commit-Queue: Hugo Holgersson <hugoh@vewd.com>
Reviewed-by: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#606480}

third_party/blink/renderer/core/page/focus_controller.cc

@@ -1226,7 +1226,6 @@ bool FocusController::SetFocusedElement(Element* element,
       new_document->FocusedElement() == element)
     return true;
 
-
   if (old_document && old_document != new_document)
     old_document->ClearFocusedElement();
 
@@ -1285,18 +1284,15 @@ static void UpdateFocusCandidateIfNeeded(WebFocusType direction,
        candidate.rect_in_root_frame.IsEmpty()))
     return;
 
-  // Ignore off screen child nodes of containers that do not scroll
-  // (overflow:hidden)
-  if (candidate.is_offscreen && !CanBeScrolledIntoView(direction, candidate))
+  // Ignore off-screen focusables that are not exposed after one "scroll step"
+  // in the direction.
+  if (candidate.is_offscreen && candidate.is_offscreen_after_scrolling)
     return;
 
   DistanceDataForNode(direction, current, candidate);
   if (candidate.distance == MaxDistance())
     return;
 
-  if (candidate.is_offscreen_after_scrolling)
-    return;
-
   if (closest.IsNull()) {
     closest = candidate;
     return;

third_party/blink/renderer/core/page/spatial_navigation.cc

@@ -667,37 +667,6 @@ void DistanceDataForNode(WebFocusType direction,
                        weighted_orthogonal_axis_distance - sqrt(overlap);
 }
 
-bool CanBeScrolledIntoView(WebFocusType direction,
-                           const FocusCandidate& candidate) {
-  DCHECK(candidate.visible_node);
-  DCHECK(candidate.is_offscreen);
-  LayoutRect candidate_rect = candidate.rect_in_root_frame;
-  // TODO(ecobos@igalia.com): Investigate interaction with Shadow DOM.
-  for (Node& parent_node :
-       NodeTraversal::AncestorsOf(*candidate.visible_node)) {
-    if (UNLIKELY(!parent_node.GetLayoutObject())) {
-      DCHECK(parent_node.IsElementNode() &&
-             ToElement(parent_node).HasDisplayContentsStyle());
-      continue;
-    }
-
-    LayoutRect parent_rect = NodeRectInRootFrame(&parent_node);
-    if (!candidate_rect.Intersects(parent_rect)) {
-      if (((direction == kWebFocusTypeLeft ||
-            direction == kWebFocusTypeRight) &&
-           parent_node.GetLayoutObject()->Style()->OverflowX() ==
-               EOverflow::kHidden) ||
-          ((direction == kWebFocusTypeUp || direction == kWebFocusTypeDown) &&
-           parent_node.GetLayoutObject()->Style()->OverflowY() ==
-               EOverflow::kHidden))
-        return false;
-    }
-    if (parent_node == candidate.enclosing_scrollable_box)
-      return CanScrollInDirection(&parent_node, direction);
-  }
-  return true;
-}
-
 // Returns a thin rectangle that represents one of box's sides.
 LayoutRect OppositeEdge(WebFocusType side,
                         const LayoutRect& box,

third_party/blink/renderer/core/page/spatial_navigation.h

@@ -93,7 +93,6 @@ CORE_EXPORT bool IsScrollableAreaOrDocument(const Node*);
 CORE_EXPORT Node* ScrollableAreaOrDocumentOf(Node*);
 bool CanScrollInDirection(const Node* container, WebFocusType);
 bool CanScrollInDirection(const LocalFrame*, WebFocusType);
-bool CanBeScrolledIntoView(WebFocusType, const FocusCandidate&);
 bool AreElementsOnSameLine(const FocusCandidate& first_candidate,
                            const FocusCandidate& second_candidate);
 void DistanceDataForNode(WebFocusType,