Fix AXTreeManager type confusion in AXPlatformNodeTextRangeProviderWin

In `AXPlatformNodeTextRangeProviderWin::GetOwner`, there is an
assumption that the position's tree is an `AXPlatformTreeManager`, but
there are some cases (Views) where this is not currently the case.
In those cases, we can't safely cast to `AXPlatformTreeManager`.

This change adds a virtual method to determine whether an AXTreeManager
is an AXPlatformTreeManager to allow us to safely cast.

(cherry picked from commit 028d1e2)

Fixed: 1451763
Change-Id: I65ebae42d200aaddbfe914e54a2c5fcb69974205
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4599972
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Benjamin Beaudry <benjamin.beaudry@microsoft.com>
Commit-Queue: Kurt Catti-Schmidt <kschmi@microsoft.com>
Cr-Original-Commit-Position: refs/heads/main@{#1155268}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4605023
Auto-Submit: Kurt Catti-Schmidt <kschmi@microsoft.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/5790@{#553}
Cr-Branched-From: 1d71a33-refs/heads/main@{#1148114}

ui/accessibility/ax_tree_manager.cc

@@ -143,6 +143,10 @@ AXTreeID AXTreeManager::GetParentTreeID() const {
   return ax_tree_ ? ax_tree_->data().parent_tree_id : AXTreeIDUnknown();
 }
 
+bool AXTreeManager::IsPlatformTreeManager() const {
+  return false;
+}
+
 AXNode* AXTreeManager::GetRoot() const {
   return ax_tree_ ? ax_tree_->root() : nullptr;
 }

ui/accessibility/ax_tree_manager.h

@@ -16,9 +16,10 @@ namespace ui {
 class AXNode;
 class AXTreeManagerMap;
 
-// Abstract interface for a class that owns an AXTree and manages its
-// connections to other AXTrees in the same page or desktop (parent and child
-// trees).
+// Interface for a class that owns an AXTree and manages its connections
+// to other AXTrees in the same page or desktop (parent and child trees)
+// as well as a mapping of AXNode's by ID for supporting `GetNodeFromTree`
+// and related methods.
 //
 // Note, the tree manager may be created for a tree which has unknown (not
 // valid) tree id. A such tree is not registered with the tree map and thus
@@ -86,6 +87,10 @@ class AX_EXPORT AXTreeManager : public AXTreeObserver {
   // Returns AXTreeIDUnknown if this tree doesn't have a parent tree.
   virtual AXTreeID GetParentTreeID() const;
 
+  // Whether this manager can access platform nodes. Defaults to false
+  // and is overridden in `AXPlatformTreeManager` to return true.
+  virtual bool IsPlatformTreeManager() const;
+
   // Returns the AXNode that is at the root of the current tree.
   AXNode* GetRoot() const;
 

ui/accessibility/platform/BUILD.gn

@@ -47,6 +47,7 @@ component("platform") {
     "child_iterator_base.h",
 
     # Used by browser_accessibility_manager.cc.
+    "ax_platform_tree_manager.cc",
     "ax_platform_tree_manager.h",
 
     # Used by browser_accessibility.cc.

ui/accessibility/platform/ax_platform_node_textrangeprovider_win.cc

@@ -1213,7 +1213,7 @@ std::u16string AXPlatformNodeTextRangeProviderWin::GetString(
 }
 
 AXPlatformNodeWin* AXPlatformNodeTextRangeProviderWin::GetOwner() const {
-  // Unit tests can't call |GetPlatformNodeFromTree|, so they must provide an
+  // Unit tests can't call `GetPlatformNodeFromTree`, so they must provide an
   // owner node.
   if (owner_for_test_.Get())
     return owner_for_test_.Get();
@@ -1227,14 +1227,16 @@ AXPlatformNodeWin* AXPlatformNodeTextRangeProviderWin::GetOwner() const {
   const AXNode* anchor = position->GetAnchor();
   DCHECK(anchor);
   const AXTreeManager* ax_tree_manager = position->GetManager();
-  DCHECK(ax_tree_manager);
+  if (ax_tree_manager && ax_tree_manager->IsPlatformTreeManager()) {
+    const AXPlatformTreeManager* platform_tree_manager =
+        static_cast<const AXPlatformTreeManager*>(ax_tree_manager);
+    DCHECK(platform_tree_manager);
 
-  const AXPlatformTreeManager* platform_tree_manager =
-      static_cast<const AXPlatformTreeManager*>(ax_tree_manager);
-  DCHECK(platform_tree_manager);
+    return static_cast<AXPlatformNodeWin*>(
+        platform_tree_manager->GetPlatformNodeFromTree(*anchor));
+  }
 
-  return static_cast<AXPlatformNodeWin*>(
-      platform_tree_manager->GetPlatformNodeFromTree(*anchor));
+  return nullptr;
 }
 
 AXPlatformNodeDelegate* AXPlatformNodeTextRangeProviderWin::GetDelegate(

ui/accessibility/platform/ax_platform_tree_manager.cc

@@ -0,0 +1,13 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/accessibility/platform/ax_platform_tree_manager.h"
+
+namespace ui {
+
+bool AXPlatformTreeManager::IsPlatformTreeManager() const {
+  return true;
+}
+
+}  // namespace ui

ui/accessibility/platform/ax_platform_tree_manager.h

@@ -15,9 +15,9 @@ namespace ui {
 class AXPlatformNode;
 class AXPlatformNodeDelegate;
 
-// Abstract interface for a class that owns an AXTree and manages its
-// connections to other AXTrees in the same page or desktop (parent and child
-// trees).
+// Abstract interface for a class that manages AXPlatformNodes and is
+// able to query for them via `GetPlatformNodeFromTree`. Extends
+// AXTreeManager, so AXNodes are also managed.
 class COMPONENT_EXPORT(AX_PLATFORM) AXPlatformTreeManager
     : public AXTreeManager {
  public:
@@ -32,6 +32,8 @@ class COMPONENT_EXPORT(AX_PLATFORM) AXPlatformTreeManager
   // of the accessibility tree.
   virtual AXPlatformNodeDelegate* RootDelegate() const = 0;
 
+  bool IsPlatformTreeManager() const override;
+
  protected:
   explicit AXPlatformTreeManager(std::unique_ptr<AXTree> tree)
       : AXTreeManager(std::move(tree)) {}