Math tag is not exposed in Accessibility.

This CL will return MathRole from blink to chromium for math tag.

BUG=429476

Review URL: https://codereview.chromium.org/722653002

git-svn-id: svn://svn.chromium.org/blink/trunk@185264 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/modules/accessibility/AXRenderObject.cpp

@@ -368,6 +368,9 @@ AccessibilityRole AXRenderObject::determineAccessibilityRole()
     if (node && node->hasTagName(dtTag))
         return DescriptionListTermRole;
 
+    if (node && (node->nodeName() == "math"))
+        return MathRole;
+
     if (node && (node->hasTagName(rpTag) || node->hasTagName(rtTag)))
         return AnnotationRole;
 
@@ -736,6 +739,9 @@ bool AXRenderObject::computeAccessibilityIsIgnored() const
     if (roleValue() == DetailsRole)
         return false;
 
+    if (roleValue() == MathRole)
+        return false;
+
     if (roleValue() == MeterRole)
         return false;