ARIA state/property aria-pressed is not exposed(Blink).

Source/modules/accessibility/AXNodeObject.cpp

Index: Source/modules/accessibility/AXNodeObject.cpp
diff --git a/Source/modules/accessibility/AXNodeObject.cpp b/Source/modules/accessibility/AXNodeObject.cpp
index 151bb67176eda090b410c3d42c3c3fd1d72b8158..95e3aad7f3a155e23432d2e12d51f9a0bde6a761 100644
--- a/Source/modules/accessibility/AXNodeObject.cpp
+++ b/Source/modules/accessibility/AXNodeObject.cpp
@@ -755,9 +755,10 @@ bool AXNodeObject::isPressed() const
     if (!node)
         return false;
 
-    // If this is an ARIA button, check the aria-pressed attribute rather than node()->active()
-    if (ariaRoleAttribute() == ButtonRole) {
-        if (equalIgnoringCase(getAttribute(aria_pressedAttr), "true"))
+    // ARIA button with aria-pressed not undefined, then check for aria-pressed attribute rather than node()->active()
+    if (ariaRoleAttribute() == ToggleButtonRole) {
+        if (equalIgnoringCase(getAttribute(aria_pressedAttr), "true")
+            || equalIgnoringCase(getAttribute(aria_pressedAttr), "mixed"))
             return true;
         return false;
     }