[mac] Send the system spellchecker language to the renderer.

chrome/browser/spellchecker/spellcheck_platform.h

Index: chrome/browser/spellchecker/spellcheck_platform.h
diff --git a/chrome/browser/spellchecker/spellcheck_platform.h b/chrome/browser/spellchecker/spellcheck_platform.h
index 4a7a6c9ed86a1aeae8c56b59dfe7a7624a0f874d..ed8d587462a6706660e46589043254ee89679b17 100644
--- a/chrome/browser/spellchecker/spellcheck_platform.h
+++ b/chrome/browser/spellchecker/spellcheck_platform.h
@@ -31,6 +31,9 @@ typedef base::Callback<void(
 // Chromium style codes (en-US not en_US). See spellchecker.cc for a full list.
 void GetAvailableLanguages(std::vector<std::string>* spellcheck_languages);
 
+// Returns the language used for spellchecking on the platform.
+std::string GetSpellCheckerLanguage();
+
 // Returns true if there is a platform-specific spellchecker that can be used.
 bool SpellCheckerAvailable();