Take 2 at implementing activeTab.

chrome/common/extensions/url_pattern_set.h

Index: chrome/common/extensions/url_pattern_set.h
diff --git a/chrome/common/extensions/url_pattern_set.h b/chrome/common/extensions/url_pattern_set.h
index c912558834058875b7fe565e02e56427023fd372..fb9c556fc6870231dd4dedf025b2d677225d1f5d 100644
--- a/chrome/common/extensions/url_pattern_set.h
+++ b/chrome/common/extensions/url_pattern_set.h
@@ -40,6 +40,10 @@ class URLPatternSet {
                           const URLPatternSet& set2,
                           URLPatternSet* out);
 
+  // Clears |out| and populates it with the union of all sets in |sets|.
+  static void CreateUnion(const std::vector<URLPatternSet>& sets,
+                          URLPatternSet* out);
+
   URLPatternSet();
   URLPatternSet(const URLPatternSet& rhs);
   explicit URLPatternSet(const std::set<URLPattern>& patterns);
@@ -49,6 +53,7 @@ class URLPatternSet {
   bool operator==(const URLPatternSet& rhs) const;
 
   bool is_empty() const;
+  size_t size() const;
   const std::set<URLPattern>& patterns() const { return patterns_; }
   const_iterator begin() const { return patterns_.begin(); }
   const_iterator end() const { return patterns_.end(); }