Disallow tabsToLinks setting to prevent tabbing to anchor with tabIndex.

Source/core/html/HTMLAnchorElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  * Copyright (C) 2003, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 119 matching lines @@
     if (isLink())
         // Only allow links with tabIndex or contentEditable to be mouse focusable.
         return HTMLElement::supportsFocus();
 
     // Allow tab index etc to control focus.
     return HTMLElement::isMouseFocusable();
 }
 
 bool HTMLAnchorElement::isKeyboardFocusable(KeyboardEvent* event) const
 {
-    if (!isLink())
+    if (!isFocusable())
+        return false;
+
+    // If tab index set explicitly, decide focus regardless of the tabsToLinks setting.

[dmazzoni, 2013/08/01 21:48:15]

Well, technically you're also skipping the test that document()->page() exists,
and the canvas subtree and hasNonEmptyBoundingBox tests.

I think bypassing the canvas subtree and hasNonEmptyBoundingBox tests  make
sense, but you should mention that in the comment, something more like:

// If the tab index is set explicitly, ignore the tabsToLinks
// setting and empty bounding box check.

Is there ever a case when the page doesn't exist, or is that just
a defensive test?

[rchl, 2013/08/20 17:58:10]

I can't say for sure but the first "!isLink()" condition that I've removed could
also return true without checking if page existed so I guess it was fine. It
seems like the 'page' variable is used solely for the tabsToLinks check and
probably the code is just being defensive.

+    if (Element::supportsFocus())
         return HTMLElement::isKeyboardFocusable(event);
 
-    if (!isFocusable())
-        return false;
-    
     Page* page = document()->page();
     if (!page)
         return false;
 
     if (!page->chrome()->client()->tabsToLinks())
         return false;
 
     if (isInCanvasSubtree())
         return true;
 
@@ skipping 591 matching lines @@
         HistogramSupport::histogramCustomCounts("MouseEventPrefetch.TapDownDuration_Click", tapDownDuration * 1000, 0, 10000, 100);
     }
 
     int flags = (m_hadTapUnconfirmed ? 2 : 0) | (capturedTapDown ? 1 : 0);
     HistogramSupport::histogramEnumeration("MouseEventPrefetch.PreTapEventsFollowedByClick", flags, 4);
 
     reset();
 }
 
 }