Keep a separate list of :host(-context) rules.

Source/core/css/RuleSetTest.cpp

 /*
  * Copyright (c) 2014, 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 118 matching lines @@
 
     helper.addCSSRules("div::content { }");
     RuleSet& ruleSet = helper.ruleSet();
     AtomicString str("div");
     const TerminatedArray<RuleData>* rules = ruleSet.tagRules(str);
     ASSERT_EQ(1u, rules->size());
     AtomicString valueStr("content");
     ASSERT_EQ(valueStr, rules->at(0).selector().value());
 }
 
+TEST(RuleSetTest, findBestRuleSetAndAdd_Host)
+{
+    CSSTestHelper helper;
+
+    helper.addCSSRules(":host { }");
+    RuleSet& ruleSet = helper.ruleSet();
+    const Vector<RuleData>* rules = ruleSet.shadowHostRules();
+    ASSERT_EQ(1u, rules->size());
+}
+
+TEST(RuleSetTest, findBestRuleSetAndAdd_HostWithId)
+{
+    CSSTestHelper helper;
+
+    helper.addCSSRules(":host(#x) { }");
+    RuleSet& ruleSet = helper.ruleSet();
+    const Vector<RuleData>* rules = ruleSet.shadowHostRules();
+    ASSERT_EQ(1u, rules->size());
+}

[kochi, 2014/12/12 09:54:40]

How about adding a test for ".foo:host {}" will result in 
rules->size() == 0 (for both :host and :host-context())?

[rune, 2014/12/12 15:44:02]

Done.

+
+TEST(RuleSetTest, findBestRuleSetAndAdd_HostContext)
+{
+    CSSTestHelper helper;
+
+    helper.addCSSRules(":host-context(*) { }");
+    RuleSet& ruleSet = helper.ruleSet();
+    const Vector<RuleData>* rules = ruleSet.shadowHostRules();
+    ASSERT_EQ(1u, rules->size());
+}
+
+TEST(RuleSetTest, findBestRuleSetAndAdd_HostContextWithId)
+{
+    CSSTestHelper helper;
+
+    helper.addCSSRules(":host-context(#x) { }");
+    RuleSet& ruleSet = helper.ruleSet();
+    const Vector<RuleData>* rules = ruleSet.shadowHostRules();
+    ASSERT_EQ(1u, rules->size());
+}
+
+TEST(RuleSetTest, findBestRuleSetAndAdd_HostAndHostContextNotInRightmost)
+{
+    CSSTestHelper helper;
+
+    helper.addCSSRules(":host-context(#x) .y, :host(.a) > #b  { }");
+    RuleSet& ruleSet = helper.ruleSet();
+    const Vector<RuleData>* shadowRules = ruleSet.shadowHostRules();
+    const TerminatedArray<RuleData>* idRules = ruleSet.idRules("b");
+    const TerminatedArray<RuleData>* classRules = ruleSet.classRules("y");
+    ASSERT_EQ(0u, shadowRules->size());
+    ASSERT_EQ(1u, idRules->size());
+    ASSERT_EQ(1u, classRules->size());
+}
+
 } // namespace blink