Take 2 at implementing activeTab.

chrome/common/extensions/url_pattern_set.cc

 // Copyright (c) 2011 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/common/extensions/url_pattern_set.h"
 
 #include <algorithm>
 #include <iterator>
 
 #include "base/logging.h"
@@ skipping 58 matching lines @@
 }
 
 bool URLPatternSet::operator==(const URLPatternSet& other) const {
   return patterns_ == other.patterns_;
 }
 
 bool URLPatternSet::is_empty() const {
   return patterns_.empty();
 }
 
+size_t URLPatternSet::size() const {
+  return patterns_.size();
+}
+
 void URLPatternSet::AddPattern(const URLPattern& pattern) {
   patterns_.insert(pattern);
 }
 
 void URLPatternSet::ClearPatterns() {
   patterns_.clear();
 }
 
 bool URLPatternSet::Contains(const URLPatternSet& set) const {
   return std::includes(patterns_.begin(), patterns_.end(),
@@ skipping 63 matching lines @@
       return false;
     }
     if (!allow_file_access && pattern.MatchesScheme(chrome::kFileScheme)) {
       pattern.SetValidSchemes(
           pattern.valid_schemes() & ~URLPattern::SCHEME_FILE);
     }
     AddPattern(pattern);
   }
   return true;
 }