Refactor GetEnclosingElement

This CL is just a simple refactor of
AXPlatformNodeTextRangeProviderWin::GetEnclosingElement. It introduces
GetLowestAccessibleCommonPlatformNode, which returns the lowest common
accessible platform node for a range.

I think the refactor makes this method a bit easier to understand.

Bug: 928948
Change-Id: Ic8bd371d076505c14961c9ec79ccb43943c5a3b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2068925Reviewed-by: Kurt Catti-Schmidt <kschmi@microsoft.com>
Commit-Queue: Benjamin Beaudry <benjamin.beaudry@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#744336}

ui/accessibility/platform/ax_platform_node_textrangeprovider_win.cc

@@ -554,22 +554,10 @@ HRESULT AXPlatformNodeTextRangeProviderWin::GetEnclosingElement(
   WIN_ACCESSIBILITY_API_HISTOGRAM(UMA_API_TEXTRANGE_GETENCLOSINGELEMENT);
   UIA_VALIDATE_TEXTRANGEPROVIDER_CALL_1_OUT(element);
 
-  AXNode* common_anchor = start_->LowestCommonAnchor(*end_);
-  DCHECK(common_anchor);
-  if (!common_anchor)
+  AXPlatformNodeWin* enclosing_node = GetLowestAccessibleCommonPlatformNode();
+  if (!enclosing_node)
     return UIA_E_ELEMENTNOTAVAILABLE;
 
-  const AXTreeID tree_id = common_anchor->tree()->GetAXTreeID();
-  const AXNode::AXID node_id = common_anchor->id();
-  AXPlatformNodeWin* enclosing_node =
-      static_cast<AXPlatformNodeWin*>(AXPlatformNode::FromNativeViewAccessible(
-          GetDelegate(tree_id, node_id)->GetNativeViewAccessible()));
-  DCHECK(enclosing_node);
-  // If this node has an ancestor that is a control type, use that as the
-  // enclosing element.
-  enclosing_node = enclosing_node->GetLowestAccessibleElement();
-  DCHECK(enclosing_node);
-
   while (enclosing_node->GetData().IsIgnored() ||
          enclosing_node->GetData().role == ax::mojom::Role::kInlineTextBox) {
     AXPlatformNodeWin* parent = static_cast<AXPlatformNodeWin*>(
@@ -1265,4 +1253,21 @@ void AXPlatformNodeTextRangeProviderWin::ValidateStartAndEndPositions() {
     end_->SnapToMaxTextOffsetIfBeyond();
 }
 
+AXPlatformNodeWin*
+AXPlatformNodeTextRangeProviderWin::GetLowestAccessibleCommonPlatformNode()
+    const {
+  AXNode* common_anchor = start_->LowestCommonAnchor(*end_);
+  if (!common_anchor)
+    return nullptr;
+
+  const AXTreeID tree_id = common_anchor->tree()->GetAXTreeID();
+  const AXNode::AXID node_id = common_anchor->id();
+  AXPlatformNodeWin* platform_node =
+      static_cast<AXPlatformNodeWin*>(AXPlatformNode::FromNativeViewAccessible(
+          GetDelegate(tree_id, node_id)->GetNativeViewAccessible()));
+  DCHECK(platform_node);
+
+  return platform_node->GetLowestAccessibleElement();
+}
+
 }  // namespace ui

ui/accessibility/platform/ax_platform_node_textrangeprovider_win.h

@@ -160,6 +160,7 @@ class AX_EXPORT __declspec(uuid("3071e40d-a10d-45ff-a59f-6e8e1138e2c1"))
   void RemoveFocusFromPreviousSelectionIfNeeded(
       const AXNodeRange& new_selection);
   void ValidateStartAndEndPositions();
+  AXPlatformNodeWin* GetLowestAccessibleCommonPlatformNode() const;
 
   Microsoft::WRL::ComPtr<AXPlatformNodeWin> owner_;
   AXPositionInstance start_;