Clean up empty namespace handling and fix empty namespaces in compound selectors

Source/core/css/CSSSelectorList.cpp

 /*
  * Copyright (C) 2008, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * 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 135 matching lines @@
             return true;
     }
 
     return false;
 }
 
 class SelectorNeedsNamespaceResolutionFunctor {
 public:
     bool operator()(const CSSSelector& selector)
     {
-        if (selector.match() == CSSSelector::Tag && selector.tagQName().prefix() != nullAtom && selector.tagQName().prefix() != starAtom)
-            return true;
-        if (selector.isAttributeSelector() && selector.attribute().prefix() != nullAtom && selector.attribute().prefix() != starAtom)
-            return true;
-        return false;
+        if (selector.match() != CSSSelector::Tag && !selector.isAttributeSelector())
+            return false;
+        const AtomicString& prefix = selector.isAttributeSelector() ? selector.attribute().prefix() : selector.tagQName().prefix();
+        return prefix != nullAtom && prefix != emptyAtom && prefix != starAtom;
     }
 };
 
 bool CSSSelectorList::selectorsNeedNamespaceResolution()
 {
     SelectorNeedsNamespaceResolutionFunctor functor;
     return forEachSelector(functor, this);
 }
 
 class SelectorHasShadowDistributed {
@@ skipping 32 matching lines @@
     }
 };
 
 bool CSSSelectorList::selectorNeedsUpdatedDistribution(size_t index) const
 {
     SelectorNeedsUpdatedDistribution functor;
     return forEachTagSelector(functor, selectorAt(index));
 }
 
 } // namespace blink