Expose internal treegrid role, do some cleanup for table/grid/treegrid handling

content/browser/accessibility/browser_accessibility_cocoa.mm

Index: content/browser/accessibility/browser_accessibility_cocoa.mm
diff --git a/content/browser/accessibility/browser_accessibility_cocoa.mm b/content/browser/accessibility/browser_accessibility_cocoa.mm
index aeb609262e23c16ea0b9ab00eed6972f905fff7d..492fd721e73cc8ca90a2f1f210f6b1ff7c8d5f22 100644
--- a/content/browser/accessibility/browser_accessibility_cocoa.mm
+++ b/content/browser/accessibility/browser_accessibility_cocoa.mm
@@ -778,8 +778,7 @@ NSString* const NSAccessibilityRequiredAttribute = @"AXRequired";
 - (NSArray*)columnHeaders {
   if (![self instanceActive])
     return nil;
-  if ([self internalRole] != ui::AX_ROLE_TABLE &&
-      [self internalRole] != ui::AX_ROLE_GRID) {
+  if (!browserAccessibility_->IsTableOrGridOrTreeGridRole()) {
     return nil;
   }
 
@@ -1007,8 +1006,7 @@ NSString* const NSAccessibilityRequiredAttribute = @"AXRequired";
   if (![self instanceActive])
     return nil;
   int headerElementId = -1;
-  if ([self internalRole] == ui::AX_ROLE_TABLE ||
-      [self internalRole] == ui::AX_ROLE_GRID) {
+  if (browserAccessibility_->IsTableOrGridOrTreeGridRole()) {
     browserAccessibility_->GetIntAttribute(
         ui::AX_ATTR_TABLE_HEADER_ID, &headerElementId);
   } else if ([self internalRole] == ui::AX_ROLE_COLUMN) {
@@ -1516,8 +1514,7 @@ NSString* const NSAccessibilityRequiredAttribute = @"AXRequired";
 - (NSArray*)rowHeaders {
   if (![self instanceActive])
     return nil;
-  if ([self internalRole] != ui::AX_ROLE_TABLE &&
-      [self internalRole] != ui::AX_ROLE_GRID) {
+  if (!browserAccessibility_->IsTableOrGridOrTreeGridRole()) {
     return nil;
   }