Implement /content/ combinator.

Source/core/css/CSSSelectorTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/css/CSSTestHelper.h"
 #include "core/css/RuleSet.h"
 
 #include <gtest/gtest.h>
 
 namespace WebCore {
 
 TEST(CSSSelector, Representations)
 {
     CSSTestHelper helper;
 
     const char* cssRules =
     "summary::-webkit-details-marker { }"
     "* {}"
     "div {}"
     "#id {}"
     ".class {}"
     "[attr] {}"
     "div:hover {}"
     "div:nth-child(2){}"
     ".class#id { }"
     "#id.class { }"
     "[attr]#id { }"
     "div[attr]#id { }"
-    "div::content { }"
+    "video::cue { }"
     "div::first-line { }"
     ".a.b.c { }"
     "div:not(.a) { }" // without class a
     "div:not(:visited) { }" // without the visited pseudo class
 
     "[attr=\"value\"] { }" // Exact equality
     "[attr~=\"value\"] { }" // One of a space-separated list
     "[attr^=\"value\"] { }" // Begins with
     "[attr$=\"value\"] { }" // Ends with
     "[attr*=\"value\"] { }" // Substring equal to
     "[attr|=\"value\"] { }" // One of a hyphen-separated list
 
     ".a .b { }" // .b is a descendant of .a
     ".a > .b { }" // .b is a direct descendant of .a
     ".a ~ .b { }" // .a precedes .b in sibling order
     ".a + .b { }" // .a element immediately precedes .b in sibling order
     ".a, .b { }" // matches .a or .b
 
     ".a.b .c {}";
 
     helper.addCSSRules(cssRules);
     EXPECT_EQ(30u, helper.ruleSet().ruleCount()); // .a, .b counts as two rules.
 #ifndef NDEBUG
     helper.ruleSet().show();
 #endif
 }
 
 } // namespace WebCore