Fix lifetime problems in AXPlatformNodeCocoa.

ui/views/widget/native_widget_mac_accessibility_unittest.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <memory>
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/mac_util.h"
 #import "base/mac/sdk_forward_declarations.h"
@@ skipping 122 matching lines @@
   gfx::Rect GetWidgetBounds() { return widget_->GetClientAreaBoundsInScreen(); }
 
  private:
   Widget* widget_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(NativeWidgetMacAccessibilityTest);
 };
 
 }  // namespace
 
+// Test that all methods in the NSAccessibility informal protocol can be called
+// on a retained accessibility object after the source view is deleted.
+TEST_F(NativeWidgetMacAccessibilityTest, Lifetime) {
+  Textfield* view = AddChildTextfield(widget()->GetContentsView()->size());
+  base::scoped_nsobject<NSObject> ax_node(view->GetNativeViewAccessible(),
+                                          base::scoped_policy::RETAIN);
+
+  NSString* kAttribute = NSAccessibilityValueAttribute;
+  NSString* kAction = NSAccessibilityShowMenuAction;
+
+  EXPECT_TRUE(
+      [[ax_node accessibilityAttributeNames] containsObject:kAttribute]);
+  EXPECT_NSEQ(kTestStringValue,
+              [ax_node accessibilityAttributeValue:kAttribute]);
+  EXPECT_TRUE([ax_node accessibilityIsAttributeSettable:kAttribute]);
+  EXPECT_TRUE([[ax_node accessibilityActionNames] containsObject:kAction]);
+  EXPECT_FALSE([ax_node accessibilityIsIgnored]);
+
+  // Not implemented, but be sure to update this test if it ever is.
+  EXPECT_FALSE(
+      [ax_node respondsToSelector:@selector(accessibilityActionDescription:)]);
+
+  // The following are also "not implemented", but the informal protocol
+  // category provides a default implementation.
+  EXPECT_EQ(NSNotFound, [ax_node accessibilityIndexOfChild:nil]);
+
+  // Note: Test -accessibilityAttributeValue:forParameter: as well, if there
+  // ever is a parameterized attribute. Otherwise it's impossible to call
+  // without throwing an exception.
+  EXPECT_EQ(@[], [ax_node accessibilityParameterizedAttributeNames]);
+
+  // The only usually available array attribute is AXChildren, so go up a level
+  // to the Widget to test that a bit. The default implementation just gets the
+  // attribute normally and returns its size (if it's an array).
+  NSString* kChildren = NSAccessibilityChildrenAttribute;
+  base::scoped_nsobject<NSObject> ax_parent(
+      [ax_node accessibilityAttributeValue:NSAccessibilityParentAttribute],
+      base::scoped_policy::RETAIN);
+  EXPECT_EQ(1u, [ax_parent accessibilityArrayAttributeCount:kChildren]);
+  EXPECT_EQ(
+      ax_node.get(),
+      [ax_parent accessibilityArrayAttributeValues:kChildren index:0
+                                          maxCount:1][0]);
+
+  // If it is not an array, the default implementation throws an exception, so
+  // it's impossible to test these methods further on |ax_node|, apart from the
+  // following, before deleting the view.
+  EXPECT_EQ(0u, [ax_node accessibilityArrayAttributeCount:kChildren]);
+
+  delete view;
+
+  EXPECT_TRUE(
+      [ax_node respondsToSelector:@selector(accessibilityAttributeNames)]);
+  EXPECT_EQ(@[], [ax_node accessibilityAttributeNames]);
+  EXPECT_EQ(nil, [ax_node accessibilityAttributeValue:kAttribute]);
+  EXPECT_FALSE([ax_node accessibilityIsAttributeSettable:kAttribute]);
+  [ax_node accessibilitySetValue:kTestStringValue forAttribute:kAttribute];
+
+  EXPECT_EQ(@[], [ax_node accessibilityActionNames]);
+  [ax_node accessibilityPerformAction:kAction];
+
+  EXPECT_TRUE([ax_node accessibilityIsIgnored]);
+  EXPECT_EQ(nil, [ax_node accessibilityHitTest:NSZeroPoint]);
+  EXPECT_EQ(nil, [ax_node accessibilityFocusedUIElement]);
+
+  // Test the attributes with default implementations provided.
+  EXPECT_EQ(NSNotFound, [ax_node accessibilityIndexOfChild:nil]);
+  EXPECT_EQ(@[], [ax_node accessibilityParameterizedAttributeNames]);
+
+  // The Widget is currently still around, but the child should be gone.
+  EXPECT_EQ(0u, [ax_parent accessibilityArrayAttributeCount:kChildren]);
+}
+
 // Check that potentially keyboard-focusable elements are always leaf nodes.
 TEST_F(NativeWidgetMacAccessibilityTest, FocusableElementsAreLeafNodes) {
   // LabelButtons will have a label inside the button. The label should be
   // ignored because the button is potentially keyboard focusable.
   TestLabelButton* button = new TestLabelButton();
   button->SetSize(widget()->GetContentsView()->size());
   widget()->GetContentsView()->AddChildView(button);
   EXPECT_NSEQ(NSAccessibilityButtonRole,
               AttributeValueAtMidpoint(NSAccessibilityRoleAttribute));
   EXPECT_EQ(
@@ skipping 548 matching lines @@
   combobox->SetSelectedIndex(1);
   EXPECT_NSEQ(@"Second Item", [ax_node AXValue]);
 
   // Expect to see both a press action and a show menu action. This matches
   // Cocoa behavior.
   EXPECT_NSEQ((@[ NSAccessibilityPressAction, NSAccessibilityShowMenuAction ]),
               [ax_node accessibilityActionNames]);
 }
 
 }  // namespace views