Use base namespace for string16 in chrome/renderer.

chrome/renderer/spellchecker/spellcheck_language.h

Index: chrome/renderer/spellchecker/spellcheck_language.h
diff --git a/chrome/renderer/spellchecker/spellcheck_language.h b/chrome/renderer/spellchecker/spellcheck_language.h
index e99e96edad5634c8c12b4ae4905346f1ecd16312..acd58f48d513abbc448dce0e5809c6702d30c77e 100644
--- a/chrome/renderer/spellchecker/spellcheck_language.h
+++ b/chrome/renderer/spellchecker/spellcheck_language.h
@@ -39,7 +39,7 @@ class SpellcheckLanguage {
                       int tag,
                       int* misspelling_start,
                       int* misspelling_len,
-                      std::vector<string16>* optional_suggestions);
+                      std::vector<base::string16>* optional_suggestions);
 
   // Initialize |spellcheck_| if that hasn't happened yet.
   bool InitializeIfNeeded();
@@ -52,7 +52,7 @@ class SpellcheckLanguage {
 
   // Returns whether or not the given word is a contraction of valid words
   // (e.g. "word:word").
-  bool IsValidContraction(const string16& word, int tag);
+  bool IsValidContraction(const base::string16& word, int tag);
 
   // Represents character attributes used for filtering out characters which
   // are not supported by this SpellCheck object.