Disable the focus moves to an element which doesn't satisfy the spec.

Source/core/page/FocusController.cpp

 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nuanti Ltd.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 564 matching lines @@
         int tabIndex = adjustedTabIndex(start);
         // If a node is excluded from the normal tabbing cycle, the next focusable node is determined by tree order
         if (tabIndex < 0) {
             for (Node* node = NodeTraversal::next(*start); node; node = NodeTraversal::next(*node)) {
                 if (shouldVisit(node) && adjustedTabIndex(node) >= 0)
                     return node;
             }
         }
 
         // First try to find a node with the same tabindex as start that comes after start in the scope.
-        if (Node* winner = findNodeWithExactTabIndex(NodeTraversal::next(*start), tabIndex, FocusTypeForward))
-            return winner;
-
+        if (tabIndex >= 0) {

[hayato, 2014/08/26 07:34:56]

You can use `else` here rather than repeating `if`.


if (tabIndex < 0) {
  ...
} else {
  ...
}

would be better than


if (tabIndex < 0) {
  ...
}
if (tabIndex >= 0) {
  ...
}

+            if (Node* winner = findNodeWithExactTabIndex(NodeTraversal::next(*start), tabIndex, FocusTypeForward))
+                return winner;
+        }
         if (!tabIndex)
             // We've reached the last node in the document with a tabindex of 0. This is the end of the tabbing order.
             return 0;
     }
 
     // Look for the first node in the scope that:
     // 1) has the lowest tabindex that is higher than start's tabindex (or 0, if start is null), and
     // 2) comes first in the scope, if there's a tie.
     if (Node* winner = nextNodeWithGreaterTabIndex(scope.rootNode(), start ? adjustedTabIndex(start) : 0))
         return winner;
@@ skipping 23 matching lines @@
     }
 
     // However, if a node is excluded from the normal tabbing cycle, the previous focusable node is determined by tree order
     if (startingTabIndex < 0) {
         for (Node* node = startingNode; node; node = NodeTraversal::previous(*node)) {
             if (shouldVisit(node) && adjustedTabIndex(node) >= 0)
                 return node;
         }
     }
 
-    if (Node* winner = findNodeWithExactTabIndex(startingNode, startingTabIndex, FocusTypeBackward))
-        return winner;
+    if (startingTabIndex >= 0) {

[hayato, 2014/08/26 07:34:56]

Ditto.

+        if (Node* winner = findNodeWithExactTabIndex(startingNode, startingTabIndex, FocusTypeBackward))
+            return winner;
+    }
 
     // There are no nodes before start with the same tabindex as start, so look for a node that:
     // 1) has the highest non-zero tabindex (that is less than start's tabindex), and
     // 2) comes last in the scope, if there's a tie.
     startingTabIndex = (start && startingTabIndex) ? startingTabIndex : std::numeric_limits<short>::max();
     return previousNodeWithLowerTabIndex(last, startingTabIndex);
 }
 
 static bool relinquishesEditingFocus(Node *node)
 {
@@ skipping 276 matching lines @@
         startingRect = nodeRectInAbsoluteCoordinates(container, true /* ignore border */);
         container = scrollableEnclosingBoxOrParentFrameForNodeInDirection(type, container);
         if (container && container->isDocumentNode())
             toDocument(container)->updateLayoutIgnorePendingStylesheets();
     } while (!consumed && container);
 
     return consumed;
 }
 
 } // namespace blink