Add Generic, Cell, GridCell and Caption roles for visibleText computation

Allow <div> or <td> retrieval of 'visibleText' for nested <div> & <td> elements.

Author: asurdej-comcast

Source/WebCore/accessibility/AccessibilityObject.cpp

@@ -1857,6 +1857,10 @@ bool AccessibilityObject::dependsOnTextUnderElement() const
     case AccessibilityRole::RadioButton:
     case AccessibilityRole::Switch:
     case AccessibilityRole::Tab:
+    case AccessibilityRole::Generic:
+    case AccessibilityRole::Cell:
+    case AccessibilityRole::GridCell:
+    case AccessibilityRole::Caption:
         return true;
     default:
         break;