An unknown role is considered a bug, should never occur

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

Index: third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
diff --git a/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp b/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
index eb389e086c2e0d601ae68e914321c49eadd939c2..7bd014f0d2f0e0621d7de0b3b842b4b9f0cd5d37 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
+++ b/third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp
@@ -675,6 +675,7 @@ AccessibilityRole AXNodeObject::NativeAccessibilityRoleIgnoringAria() const {
   return kUnknownRole;
 }
 
+// Determine an accessibility role.

[dmazzoni, 2017/05/24 21:57:02]

This comment doesn't really add much value. :)

Either add more info (like when this is called, whether subclasses override it,
what information is or isn't included in the determination) or delete the
comment
and let the method name speak for itself

[aleventhal, 2017/05/25 17:28:34]

Yeah I'm not sure how that happened, duh. 

 AccessibilityRole AXNodeObject::DetermineAccessibilityRole() {
   if (!GetNode())
     return kUnknownRole;
@@ -685,17 +686,7 @@ AccessibilityRole AXNodeObject::DetermineAccessibilityRole() {
     return kStaticTextRole;
 
   AccessibilityRole role = NativeAccessibilityRoleIgnoringAria();
-  if (role != kUnknownRole)
-    return role;
-  if (GetNode()->IsElementNode()) {
-    Element* element = ToElement(GetNode());
-    // A generic element with tabIndex explicitly set gets GroupRole.
-    // The layout checks for focusability aren't critical here; a false
-    // positive would be harmless.
-    if (element->IsInCanvasSubtree() && element->SupportsFocus())
-      return kGenericContainerRole;
-  }
-  return kUnknownRole;
+  return role == kUnknownRole ? kGenericContainerRole : role;
 }
 
 AccessibilityRole AXNodeObject::DetermineAriaRoleAttribute() const {