Use base::STLSet* in place of std::set_* for simplicity and consistency.

extensions/common/url_pattern_set.cc

Index: extensions/common/url_pattern_set.cc
diff --git a/extensions/common/url_pattern_set.cc b/extensions/common/url_pattern_set.cc
index 118f9ee31ead02fa1891469830b54ab90698beb1..a04d6346d7e470446da5d9d3e2d670a50ff1e5e6 100644
--- a/extensions/common/url_pattern_set.cc
+++ b/extensions/common/url_pattern_set.cc
@@ -4,7 +4,6 @@
 
 #include "extensions/common/url_pattern_set.h"
 
-#include <algorithm>
 #include <iterator>
 
 #include "base/logging.h"
@@ -28,7 +27,6 @@ const char kInvalidURLPatternError[] = "Invalid url pattern '*'";
 void URLPatternSet::CreateDifference(const URLPatternSet& set1,
                                      const URLPatternSet& set2,
                                      URLPatternSet* out) {
-  out->ClearPatterns();
   out->patterns_ = base::STLSetDifference<std::set<URLPattern> >(
       set1.patterns_, set2.patterns_);
 }
@@ -37,22 +35,16 @@ void URLPatternSet::CreateDifference(const URLPatternSet& set1,
 void URLPatternSet::CreateIntersection(const URLPatternSet& set1,
                                        const URLPatternSet& set2,
                                        URLPatternSet* out) {
-  out->ClearPatterns();
-  std::set_intersection(set1.patterns_.begin(), set1.patterns_.end(),
-                        set2.patterns_.begin(), set2.patterns_.end(),
-                        std::inserter<std::set<URLPattern> >(
-                            out->patterns_, out->patterns_.begin()));
+  out->patterns_ = base::STLSetIntersection<std::set<URLPattern> >(
+      set1.patterns_, set2.patterns_);
 }
 
 // static
 void URLPatternSet::CreateUnion(const URLPatternSet& set1,
                                 const URLPatternSet& set2,
                                 URLPatternSet* out) {
-  out->ClearPatterns();
-  std::set_union(set1.patterns_.begin(), set1.patterns_.end(),
-                 set2.patterns_.begin(), set2.patterns_.end(),
-                 std::inserter<std::set<URLPattern> >(
-                     out->patterns_, out->patterns_.begin()));
+  out->patterns_ = base::STLSetUnion<std::set<URLPattern> >(
+      set1.patterns_, set2.patterns_);
 }
 
 // static