AX: Refactor OnNativeScroll* functionality to be consistent.

This patch extracts a snippet used for retrieving and updating
a layout object for scroll action into a separate function, and uses
it in the three OnNativeScroll* functions.


R=aleventhal@chromium.org, chrishtr@chromium.org

Change-Id: I68a580f7dc5887841a874fb705eeaf9da6916740
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2157671Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760961}

third_party/blink/renderer/modules/accessibility/ax_object.cc

@@ -3419,18 +3419,21 @@ bool AXObject::InternalSetAccessibilityFocusAction() {
   return false;
 }
 
-bool AXObject::OnNativeScrollToMakeVisibleAction() const {
+LayoutObject* AXObject::GetLayoutObjectForNativeScrollAction() const {
   Node* node = GetNode();
   if (!node || !node->isConnected())
-    return false;
+    return nullptr;
 
   // Node might not have a LayoutObject due to the fact that it is in a locked
   // subtree. Force the update to create the LayoutObject (and update position
   // information) for this node.
   GetDocument()->UpdateStyleAndLayoutForNode(
       node, DocumentUpdateReason::kDisplayLock);
+  return node->GetLayoutObject();
+}
 
-  LayoutObject* layout_object = node->GetLayoutObject();
+bool AXObject::OnNativeScrollToMakeVisibleAction() const {
+  LayoutObject* layout_object = GetLayoutObjectForNativeScrollAction();
   if (!layout_object)
     return false;
   PhysicalRect target_rect(layout_object->AbsoluteBoundingBoxRect());
@@ -3450,10 +3453,10 @@ bool AXObject::OnNativeScrollToMakeVisibleWithSubFocusAction(
     const IntRect& rect,
     blink::mojom::blink::ScrollAlignment horizontal_scroll_alignment,
     blink::mojom::blink::ScrollAlignment vertical_scroll_alignment) const {
-  Node* node = GetNode();
-  LayoutObject* layout_object = node ? node->GetLayoutObject() : nullptr;
-  if (!layout_object || !node->isConnected())
+  LayoutObject* layout_object = GetLayoutObjectForNativeScrollAction();
+  if (!layout_object)
     return false;
+
   PhysicalRect target_rect =
       layout_object->LocalToAbsoluteRect(PhysicalRect(rect));
   layout_object->ScrollRectToVisible(
@@ -3470,10 +3473,10 @@ bool AXObject::OnNativeScrollToMakeVisibleWithSubFocusAction(
 
 bool AXObject::OnNativeScrollToGlobalPointAction(
     const IntPoint& global_point) const {
-  Node* node = GetNode();
-  LayoutObject* layout_object = node ? node->GetLayoutObject() : nullptr;
-  if (!layout_object || !node->isConnected())
+  LayoutObject* layout_object = GetLayoutObjectForNativeScrollAction();
+  if (!layout_object)
     return false;
+
   PhysicalRect target_rect(layout_object->AbsoluteBoundingBoxRect());
   target_rect.Move(-PhysicalOffset(global_point));
   layout_object->ScrollRectToVisible(

third_party/blink/renderer/modules/accessibility/ax_object.h

@@ -1151,6 +1151,12 @@ class MODULES_EXPORT AXObject : public GarbageCollected<AXObject> {
                                             const QualifiedName&) const;
   bool IsHiddenViaStyle() const;
 
+  // Returns an updated layout object to be used in a native scroll action. Note
+  // that this updates style for `GetNode()` as well as layout for any layout
+  // objects generated. Returns nullptr if a native scroll action to the node is
+  // not possible.
+  LayoutObject* GetLayoutObjectForNativeScrollAction() const;
+
   static unsigned number_of_live_ax_objects_;
 
   DISALLOW_COPY_AND_ASSIGN(AXObject);