Treat mixed value on switch role as false

Currently, mixed (indeterminate) values are exposed as true or mixed on
the switch role. According to https://w3c.github.io/aria/#switch, they
should be exposed as false.

Bug: 1372131
Change-Id: I08ec7f764305812b9867b1083649577589052d8f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4632270
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1167552}

content/test/data/accessibility/aria/aria-switch-expected-android-external.txt

@@ -2,4 +2,4 @@ WebView focusable focused scrollable actions:[CLEAR_FOCUS, AX_FOCUS] bundle:[chr
 ++ToggleButton text:"Switch1" stateDescription:"Off" checkable clickable actions:[CLICK, AX_FOCUS, NEXT, PREVIOUS] bundle:[chromeRole="switch", roleDescription="switch"]
 ++ToggleButton text:"Switch2" stateDescription:"Off" checkable clickable actions:[CLICK, AX_FOCUS, NEXT, PREVIOUS] bundle:[chromeRole="switch", roleDescription="switch"]
 ++ToggleButton text:"Switch3" stateDescription:"On" checkable checked clickable actions:[CLICK, AX_FOCUS, NEXT, PREVIOUS] bundle:[chromeRole="switch", roleDescription="switch"]
-++ToggleButton text:"Switch4" stateDescription:"On" checkable checked clickable actions:[CLICK, AX_FOCUS, NEXT, PREVIOUS] bundle:[chromeRole="switch", roleDescription="switch"]
+++ToggleButton text:"Switch4" stateDescription:"Off" checkable clickable actions:[CLICK, AX_FOCUS, NEXT, PREVIOUS] bundle:[chromeRole="switch", roleDescription="switch"]

content/test/data/accessibility/aria/aria-switch-expected-android.txt

@@ -2,4 +2,4 @@ android.webkit.WebView focusable focused scrollable
 ++android.widget.ToggleButton role_description='switch' checkable clickable name='Switch1' state_description='Off'
 ++android.widget.ToggleButton role_description='switch' checkable clickable name='Switch2' state_description='Off'
 ++android.widget.ToggleButton role_description='switch' checkable checked clickable name='Switch3' state_description='On'
-++android.widget.ToggleButton role_description='switch' checkable checked clickable name='Switch4' state_description='On'
+++android.widget.ToggleButton role_description='switch' checkable clickable name='Switch4' state_description='Off'

content/test/data/accessibility/aria/aria-switch-expected-auralinux.txt

@@ -2,4 +2,4 @@
 ++[toggle button] name='Switch1' checkable:true xml-roles:switch
 ++[toggle button] name='Switch2' checkable:true xml-roles:switch
 ++[toggle button] name='Switch3' checked checkable:true xml-roles:switch
-++[toggle button] name='Switch4' checked checkable:true xml-roles:switch
+++[toggle button] name='Switch4' checkable:true xml-roles:switch

content/test/data/accessibility/aria/aria-switch-expected-blink.txt

@@ -10,6 +10,6 @@ rootWebArea
 ++++++switch name='Switch3' checkedState=true
 ++++++++staticText name='Switch3'
 ++++++++++inlineTextBox name='Switch3'
-++++++switch name='Switch4' checkedState=true
+++++++switch name='Switch4' checkedState=false
 ++++++++staticText name='Switch4'
 ++++++++++inlineTextBox name='Switch4'

content/test/data/accessibility/aria/aria-switch-expected-mac.txt

@@ -2,4 +2,4 @@ AXWebArea AXRoleDescription='HTML content'
 ++AXCheckBox AXSubrole=AXSwitch AXRoleDescription='switch' AXTitle='Switch1' AXValue=0
 ++AXCheckBox AXSubrole=AXSwitch AXRoleDescription='switch' AXTitle='Switch2' AXValue=0
 ++AXCheckBox AXSubrole=AXSwitch AXRoleDescription='switch' AXTitle='Switch3' AXValue=1
-++AXCheckBox AXSubrole=AXSwitch AXRoleDescription='switch' AXTitle='Switch4' AXValue=1
+++AXCheckBox AXSubrole=AXSwitch AXRoleDescription='switch' AXTitle='Switch4' AXValue=0

content/test/data/accessibility/aria/aria-switch-expected-win.txt

@@ -2,4 +2,4 @@ ROLE_SYSTEM_DOCUMENT READONLY FOCUSABLE ia2_hypertext='<obj0><obj1><obj2><obj3>'
 ++IA2_ROLE_TOGGLE_BUTTON name='Switch1' IA2_STATE_CHECKABLE xml-roles:switch checkable:true ia2_hypertext='Switch1'
 ++IA2_ROLE_TOGGLE_BUTTON name='Switch2' IA2_STATE_CHECKABLE xml-roles:switch checkable:true ia2_hypertext='Switch2'
 ++IA2_ROLE_TOGGLE_BUTTON name='Switch3' PRESSED CHECKED IA2_STATE_CHECKABLE xml-roles:switch checkable:true ia2_hypertext='Switch3'
-++IA2_ROLE_TOGGLE_BUTTON name='Switch4' PRESSED CHECKED IA2_STATE_CHECKABLE xml-roles:switch checkable:true ia2_hypertext='Switch4'
+++IA2_ROLE_TOGGLE_BUTTON name='Switch4' IA2_STATE_CHECKABLE xml-roles:switch checkable:true ia2_hypertext='Switch4'

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

@@ -2718,9 +2718,10 @@ ax::mojom::blink::CheckedState AXObject::CheckedState() const {
   const AtomicString& checked_attribute = GetAOMPropertyOrARIAAttribute(prop);
   if (checked_attribute) {
     if (EqualIgnoringASCIICase(checked_attribute, "mixed")) {
-      // Only checkable role that doesn't support mixed is the switch.
-      if (role != ax::mojom::blink::Role::kSwitch)
-        return ax::mojom::blink::CheckedState::kMixed;
+      // Mixed value is invalid for switch role. Treat as false.
+      return role == ax::mojom::blink::Role::kSwitch
+                 ? ax::mojom::blink::CheckedState::kFalse
+                 : ax::mojom::blink::CheckedState::kMixed;
     }
 
     // Anything other than "false" should be treated as "true".
@@ -2735,13 +2736,17 @@ ax::mojom::blink::CheckedState AXObject::CheckedState() const {
     if (!node)
       return ax::mojom::blink::CheckedState::kNone;
 
-    // Expose native checkbox mixed state as accessibility mixed state. However,
-    // do not expose native radio mixed state as accessibility mixed state.
-    // This would confuse the JAWS screen reader, which reports a mixed radio as
-    // both checked and partially checked, but a native mixed native radio
-    // button simply means no radio buttons have been checked in the group yet.
-    if (IsNativeCheckboxInMixedState(node))
-      return ax::mojom::blink::CheckedState::kMixed;
+    // Expose native checkbox mixed state as accessibility mixed state (unless
+    // the role is switch). However, do not expose native radio mixed state as
+    // accessibility mixed state. This would confuse the JAWS screen reader,
+    // which reports a mixed radio as both checked and partially checked, but a
+    // native mixed native radio button simply means no radio buttons have been
+    // checked in the group yet.
+    if (IsNativeCheckboxInMixedState(node)) {
+      return role == ax::mojom::blink::Role::kSwitch
+                 ? ax::mojom::blink::CheckedState::kFalse
+                 : ax::mojom::blink::CheckedState::kMixed;
+    }
 
     auto* html_input_element = DynamicTo<HTMLInputElement>(node);
     if (html_input_element && html_input_element->ShouldAppearChecked()) {

third_party/blink/web_tests/accessibility/aria-checkbox-checked-mixed.html

@@ -10,7 +10,7 @@
 <div id="element2" role="menuitemcheckbox" aria-checked="mixed"></div>
 <div id="element3" role="radio" aria-checked="mixed"></div>
 <div id="element4" role="menuitemradio" aria-checked="mixed"></div>
-<!-- Switch specifically does not support mixed -->
+<!-- Switch specifically does not support mixed. It's treated as false. -->
 <div id="element5" role="switch" aria-checked="mixed"></div>
 
 <input id="element6" type="checkbox" aria-checked="mixed" checked />
@@ -39,7 +39,7 @@
                    "mixed",
                    "mixed",
                    "mixed",
-                   "true",
+                   "false",
                    "mixed",
                    "mixed",
                    "mixed",