Add MarkRole in blink side to expose mark tag properly

Source/modules/accessibility/AXLayoutObject.cpp

Index: Source/modules/accessibility/AXLayoutObject.cpp
diff --git a/Source/modules/accessibility/AXLayoutObject.cpp b/Source/modules/accessibility/AXLayoutObject.cpp
index 283bd9f3274c09d0dd50a4681ca165d9528575ce..86389a4fc563df6604ce7ddd9fd7e34690306e24 100644
--- a/Source/modules/accessibility/AXLayoutObject.cpp
+++ b/Source/modules/accessibility/AXLayoutObject.cpp
@@ -651,6 +651,9 @@ bool AXLayoutObject::computeAccessibilityIsIgnored(IgnoredReasons* ignoredReason
     if (roleValue() == TimeRole)
         return false;
 
+    if (roleValue() == MarkRole)
+        return false;
+
     // if this element has aria attributes on it, it should not be ignored.
     if (supportsARIAAttributes())
         return false;