Use base namespace for string16 in chrome/renderer.

chrome/renderer/spellchecker/custom_dictionary_engine.h

Index: chrome/renderer/spellchecker/custom_dictionary_engine.h
diff --git a/chrome/renderer/spellchecker/custom_dictionary_engine.h b/chrome/renderer/spellchecker/custom_dictionary_engine.h
index fde49d60901eaf7f27cddecf9f2f6370077fbe18..d1f3a95fed111d4968c66a3df0eff8615d6afaf7 100644
--- a/chrome/renderer/spellchecker/custom_dictionary_engine.h
+++ b/chrome/renderer/spellchecker/custom_dictionary_engine.h
@@ -25,7 +25,7 @@ class CustomDictionaryEngine {
   // Spellcheck |text|. Assumes that another spelling engine has set
   // |misspelling_start| and |misspelling_len| to indicate a misspelling.
   // Returns true if there are no misspellings, otherwise returns false.
-  bool SpellCheckWord(const string16& text,
+  bool SpellCheckWord(const base::string16& text,
                       int misspelling_start,
                       int misspelling_len);
 
@@ -36,7 +36,7 @@ class CustomDictionaryEngine {
 
  private:
   // Correctly spelled words.
-  std::set<string16> dictionary_;
+  std::set<base::string16> dictionary_;
 
   DISALLOW_COPY_AND_ASSIGN(CustomDictionaryEngine);
 };