Reland "A11y:Expose labels of radio & checkbox when focused."

This is a reland of 9612f58a

The change was reverted because of failure on linux-trusty-rel due to
a mismatch in dump test result for "checkable" state.
In this reland, I added a filter @AURALINUX-DENY:checkable to fix this
test mismatch. This filter seems to accompany all other radio button dump
tests for linux platform.

Original change's description:
> A11y:Expose labels of radio & checkbox when focused.
>
> Currently, when a label is referenced by a control of type radio or
> checkbox, we set the label as ignored in the AXTree thereby excluding
> it from being perceived by ATs.
> However, for the case when the control (radio/checkbox) is a
> descendant of the label and label is focusable (tabindex="0") but
> control is to be omitted from focus (tabindex="-1"), ATs perceive
> neither the label nor the control when tabbing through the content:
>
>     <label style="display:block" tabindex="0">
>       radio button 1
>       <input type="radio" id="radio1" tabindex="-1">
>     </label>
>
>     <label style="display:block" for="radio2" tabindex="0">
>       radio button 2
>       <input type="radio" id="radio2" tabindex="-1">
>     </label>
>
>     <label style="display:block" for="checkbox1" tabindex="0">
>       checkbox 1
>       <input type="checkbox" id="checkbox1" tabindex="-1">
>     </label>
>
>     <label style="display:block" for="checkbox2" tabindex="0">
>       checkbox 2
>       <input type="checkbox" id="checkbox2" tabindex="-1">
>     </label>
>
> This change fixes the above scenario by exposing labels (referenced by
> radio or checkbox) when they are focusable. For all other cases when
> labels are referenced by radio or checkbox, we keep the existing
> behavior of ignoring the label.
>
> Note: Neither Firefox nor Edge legacy hides a label from AT when the
> label is referenced by a control. On Firefox and Edge legacy, label
> content will be read twice (focus on label and focus on control
> respectively).
> WAI-ARIA spec does not specify label should be ignored when associated
> with a radio/checkbox control.
>
> Bug: 1040210
> Change-Id: Ie7df5144dd2f0d285d97e6556adb46dcf2338f25
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1992017
> Commit-Queue: Victor Fei <vicfei@microsoft.com>
> Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#731820}

Bug: 1040210
Change-Id: I09243796ec3affe648d46ec64d7dd20e20c5893f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2002892Reviewed-by: Kurt Catti-Schmidt <kschmi@microsoft.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Victor Fei <vicfei@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#732931}

content/browser/accessibility/dump_accessibility_tree_browsertest.cc

@@ -1661,6 +1661,11 @@ IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilityInputRadio) {
   RunHtmlTest(FILE_PATH_LITERAL("input-radio.html"));
 }
 
+IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest,
+                       AccessibilityInputRadioCheckboxLabel) {
+  RunHtmlTest(FILE_PATH_LITERAL("input-radio-checkbox-label.html"));
+}
+
 IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest,
                        AccessibilityInputRadioInMenu) {
   RunHtmlTest(FILE_PATH_LITERAL("input-radio-in-menu.html"));

content/test/data/accessibility/html/input-radio-checkbox-label-expected-android.txt

+android.webkit.WebView focusable focused scrollable
+++android.view.View
+++++android.widget.RadioButton role_description='radio button' checkable clickable focusable name='label ignored for radio button'
+++++android.widget.CheckBox role_description='checkbox' checkable clickable focusable name='label ignored for checkbox'
+++++android.view.View focusable name='label exposed for radio button '
+++++++android.view.View name='label exposed for radio button '
+++++++android.widget.RadioButton role_description='radio button' checkable clickable focusable name='label exposed for radio button' item_index=1 row_index=1
+++++++android.view.View name=' '
+++++android.view.View focusable name='label exposed for checkbox '
+++++++android.view.View name='label exposed for checkbox '
+++++++android.widget.CheckBox role_description='checkbox' checkable clickable focusable name='label exposed for checkbox'
+++++++android.view.View name=' '

content/test/data/accessibility/html/input-radio-checkbox-label-expected-auralinux.txt

+[document web]
+++[section]
+++++[radio button] name='label ignored for radio button' checkable:true
+++++[check box] name='label ignored for checkbox' checkable:true
+++++[label] name='label exposed for radio button ' label-for
+++++++[static] name='label exposed for radio button '
+++++++[radio button] name='label exposed for radio button' labelled-by checkable:true
+++++++[static] name=' '
+++++[label] name='label exposed for checkbox ' label-for
+++++++[static] name='label exposed for checkbox '
+++++++[check box] name='label exposed for checkbox' labelled-by checkable:true
+++++++[static] name=' '

content/test/data/accessibility/html/input-radio-checkbox-label-expected-blink.txt

+rootWebArea
+++genericContainer
+++++radioButton name='label ignored for radio button' checkedState=false
+++++checkBox name='label ignored for checkbox' checkedState=false
+++++labelText name='label exposed for radio button '
+++++++staticText name='label exposed for radio button '
+++++++++inlineTextBox name='label exposed for radio button '
+++++++radioButton name='label exposed for radio button' checkedState=false
+++++++staticText name=' '
+++++++++inlineTextBox name=' '
+++++labelText name='label exposed for checkbox '
+++++++staticText name='label exposed for checkbox '
+++++++++inlineTextBox name='label exposed for '
+++++++++inlineTextBox name='checkbox '
+++++++checkBox name='label exposed for checkbox' checkedState=false
+++++++staticText name=' '

content/test/data/accessibility/html/input-radio-checkbox-label-expected-mac.txt

+AXWebArea
+++AXGroup
+++++AXRadioButton AXTitle='label ignored for radio button' AXValue='0'
+++++AXCheckBox AXTitle='label ignored for checkbox' AXValue='0'
+++++AXGroup AXTitle='label exposed for radio button '
+++++++AXStaticText AXValue='label exposed for radio button '
+++++++AXRadioButton AXValue='0' AXTitleUIElement='AXGroup label exposed for radio button '
+++++++AXStaticText AXValue=' '
+++++AXGroup AXTitle='label exposed for checkbox '
+++++++AXStaticText AXValue='label exposed for checkbox '
+++++++AXCheckBox AXValue='0' AXTitleUIElement='AXGroup label exposed for checkbox '
+++++++AXStaticText AXValue=' '

content/test/data/accessibility/html/input-radio-checkbox-label-expected-uia-win.txt

+document
+++group IsControlElement=false
+++++radio Name='label ignored for radio button' SelectionItem.IsSelected=false
+++++checkbox Name='label ignored for checkbox' Toggle.ToggleState='Off'
+++++description Name='label exposed for radio button '
+++++++description Name='label exposed for radio button '
+++++++radio Name='label exposed for radio button' SelectionItem.IsSelected=false
+++++++description Name=' '
+++++description Name='label exposed for checkbox '
+++++++description Name='label exposed for checkbox '
+++++++checkbox Name='label exposed for checkbox' Toggle.ToggleState='Off'
+++++++description Name=' '

content/test/data/accessibility/html/input-radio-checkbox-label-expected-win.txt

+ROLE_SYSTEM_DOCUMENT READONLY FOCUSABLE
+++IA2_ROLE_SECTION
+++++ROLE_SYSTEM_RADIOBUTTON name='label ignored for radio button' FOCUSABLE IA2_STATE_CHECKABLE checkable:true
+++++ROLE_SYSTEM_CHECKBUTTON name='label ignored for checkbox' FOCUSABLE IA2_STATE_CHECKABLE checkable:true
+++++IA2_ROLE_LABEL name='label exposed for radio button ' FOCUSABLE
+++++++ROLE_SYSTEM_STATICTEXT name='label exposed for radio button '
+++++++ROLE_SYSTEM_RADIOBUTTON name='label exposed for radio button' FOCUSABLE IA2_STATE_CHECKABLE checkable:true
+++++++ROLE_SYSTEM_STATICTEXT name=' '
+++++IA2_ROLE_LABEL name='label exposed for checkbox ' FOCUSABLE
+++++++ROLE_SYSTEM_STATICTEXT name='label exposed for checkbox '
+++++++ROLE_SYSTEM_CHECKBUTTON name='label exposed for checkbox' FOCUSABLE IA2_STATE_CHECKABLE checkable:true
+++++++ROLE_SYSTEM_STATICTEXT name=' '

content/test/data/accessibility/html/input-radio-checkbox-label.html

+<!--
+@AURALINUX-DENY:checkable
+-->
+<!DOCTYPE html>
+<html>
+<body>
+  <body>
+    <!-- When the radio button's associated label is not set to be
+      focusable, it will be ignored from the accessibility tree. -->
+    <label for="radio1">
+      label ignored for radio button
+      <input type="radio" id="radio1">
+    </label>
+
+    <!-- When the checkbox's associated label is not set to be
+      focusable, it will be ignored from the accessibility tree. -->
+    <label for="checkbox1">
+      label ignored for checkbox
+      <input type="checkbox" id="checkbox1">
+    </label>
+
+    <!-- When the radio button's associated label is set to be focusable,
+      it will be included in the accessibility tree. -->
+    <label for="radio2" tabindex="0">
+      label exposed for radio button
+      <input type="radio" id="radio2" tabindex="-1">
+    </label>
+
+    <!-- When the checkbox's associated label is set to be focusable,
+      it will be included in the accessibility tree. -->
+    <label for="checkbox2" tabindex="0">
+      label exposed for checkbox
+      <input type="checkbox" id="checkbox2" tabindex="-1">
+    </label>
+  </body>
+</html>

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

@@ -1735,7 +1735,8 @@ AXObject* AXLayoutObject::AccessibilityHitTest(const IntPoint& point) const {
     // control.
     if (result->IsAXLayoutObject()) {
       AXObject* control_object =
-          ToAXLayoutObject(result)->CorrespondingControlForLabelElement();
+          ToAXLayoutObject(result)
+              ->CorrespondingControlAXObjectForLabelElement();
       if (control_object && control_object->NameFromLabelElement())
         return control_object;
     }

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

@@ -178,21 +178,24 @@ AXObjectInclusion AXNodeObject::ShouldIncludeBasedOnSemantics(
   if (IsTableLikeRole() || IsTableRowLikeRole() || IsTableCellLikeRole())
     return kIncludeObject;
 
-  // Ignore labels that are already referenced by a control.
-  AXObject* control_object = CorrespondingControlForLabelElement();
-  HTMLLabelElement* label = LabelElementContainer();
-  if (control_object && control_object->IsCheckboxOrRadio() &&
-      control_object->NameFromLabelElement() &&
+  // Ignore labels that are already referenced by a control but are not set to
+  // be focusable.
+  AXObject* control_ax_object = CorrespondingControlAXObjectForLabelElement();
+  if (control_ax_object && control_ax_object->IsCheckboxOrRadio() &&
+      control_ax_object->NameFromLabelElement() &&
       AccessibleNode::GetPropertyOrARIAAttribute(
-          label, AOMStringProperty::kRole) == g_null_atom) {
+          LabelElementContainer(), AOMStringProperty::kRole) == g_null_atom) {
+    AXObject* label_ax_object = CorrespondingLabelAXObject();
+    // If the label is set to be focusable, we should expose it.
+    if (label_ax_object && label_ax_object->CanSetFocusAttribute())
+      return kIncludeObject;
+
     if (ignored_reasons) {
-      if (label && label != GetNode()) {
-        AXObject* label_ax_object = AXObjectCache().GetOrCreate(label);
+      if (label_ax_object && label_ax_object != this)
         ignored_reasons->push_back(
             IgnoredReason(kAXLabelContainer, label_ax_object));
-      }
 
-      ignored_reasons->push_back(IgnoredReason(kAXLabelFor, control_object));
+      ignored_reasons->push_back(IgnoredReason(kAXLabelFor, control_ax_object));
     }
     return kIgnoreObject;
   }
@@ -2811,7 +2814,7 @@ void AXNodeObject::SetNode(Node* node) {
   node_ = node;
 }
 
-AXObject* AXNodeObject::CorrespondingControlForLabelElement() const {
+AXObject* AXNodeObject::CorrespondingControlAXObjectForLabelElement() const {
   HTMLLabelElement* label_element = LabelElementContainer();
   if (!label_element)
     return nullptr;
@@ -2829,6 +2832,14 @@ AXObject* AXNodeObject::CorrespondingControlForLabelElement() const {
   return AXObjectCache().GetOrCreate(corresponding_control);
 }
 
+AXObject* AXNodeObject::CorrespondingLabelAXObject() const {
+  HTMLLabelElement* label_element = LabelElementContainer();
+  if (!label_element)
+    return nullptr;
+
+  return AXObjectCache().GetOrCreate(label_element);
+}
+
 HTMLLabelElement* AXNodeObject::LabelElementContainer() const {
   if (!GetNode())
     return nullptr;

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

@@ -79,7 +79,8 @@ class MODULES_EXPORT AXNodeObject : public AXObject {
   Element* MouseButtonListener() const;
   bool IsNativeCheckboxOrRadio() const;
   void SetNode(Node*);
-  AXObject* CorrespondingControlForLabelElement() const;
+  AXObject* CorrespondingControlAXObjectForLabelElement() const;
+  AXObject* CorrespondingLabelAXObject() const;
   HTMLLabelElement* LabelElementContainer() const;
 
   //