Initialize SubstringSetMatcher on construction

chrome/browser/extensions/api/declarative/substring_set_matcher_unittest.cc

 // Copyright (c) 2012 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 "chrome/browser/extensions/api/declarative/substring_set_matcher.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 146 matching lines @@
   patterns.clear();
   patterns.push_back(&pattern_2);
   matcher.UnregisterPatterns(patterns);
 
   matches.clear();
   matcher.Match("abd", &matches);
   EXPECT_EQ(1u, matches.size());
   EXPECT_TRUE(matches.end() != matches.find(1));
   EXPECT_TRUE(matches.end() == matches.find(2));
 }
+
+TEST(SubstringSetMatcherTest, TestEmptyMatcher) {
+  SubstringSetMatcher matcher;
+  std::set<int> matches;
+  matcher.Match("abd", &matches);
+  EXPECT_TRUE(matches.empty());
+}