[CleanUp] Use base::STLSetDifference in place of std::set_difference

chrome/browser/spellchecker/spellcheck_custom_dictionary.cc

Index: chrome/browser/spellchecker/spellcheck_custom_dictionary.cc
diff --git a/chrome/browser/spellchecker/spellcheck_custom_dictionary.cc b/chrome/browser/spellchecker/spellcheck_custom_dictionary.cc
index c5c8163b0e8bdfc9bf9ee053ad29979db3a7aaf5..4872b4ead81c957bc25093021d751493ae093128 100644
--- a/chrome/browser/spellchecker/spellcheck_custom_dictionary.cc
+++ b/chrome/browser/spellchecker/spellcheck_custom_dictionary.cc
@@ -129,12 +129,7 @@ void SaveDictionaryFileReliably(
 int SanitizeWordsToAdd(const WordSet& existing, WordList& to_add) {
   // Do not add duplicate words.
   std::sort(to_add.begin(), to_add.end());
-  WordList new_words;
-  std::set_difference(to_add.begin(),
-                      to_add.end(),
-                      existing.begin(),
-                      existing.end(),
-                      std::back_inserter(new_words));
+  WordList new_words = base::STLSetDifference<WordList>(to_add, existing);
   new_words.erase(std::unique(new_words.begin(), new_words.end()),
                   new_words.end());
   int result = VALID_CHANGE;
@@ -328,12 +323,8 @@ syncer::SyncMergeResult SpellcheckCustomDictionary::MergeDataAndStartSyncing(
 
   // Add as many as possible local words remotely.
   std::sort(to_add_locally.begin(), to_add_locally.end());
-  WordList to_add_remotely;
-  std::set_difference(words_.begin(),
-                      words_.end(),
-                      to_add_locally.begin(),
-                      to_add_locally.end(),
-                      std::back_inserter(to_add_remotely));
+  WordList to_add_remotely = base::STLSetDifference<WordList>(words_,
+                                                              to_add_locally);
 
   // Send local changes to the sync server.
   Change to_change_remotely(to_add_remotely);
@@ -431,12 +422,9 @@ void SpellcheckCustomDictionary::UpdateDictionaryFile(
 
   // Remove words.
   std::sort(custom_words.begin(), custom_words.end());
-  WordList remaining;
-  std::set_difference(custom_words.begin(),
-                      custom_words.end(),
-                      dictionary_change.to_remove().begin(),
-                      dictionary_change.to_remove().end(),
-                      std::back_inserter(remaining));
+  WordList remaining =
+      base::STLSetDifference<WordList>(custom_words,
+                                       dictionary_change.to_remove());
   std::swap(custom_words, remaining);
 
   SaveDictionaryFileReliably(custom_words, path);