Forward declare test class as friend of SpeechInputLocaleConfigImpl.

ios/chrome/browser/voice/speech_input_locale_config_impl.h

Index: ios/chrome/browser/voice/speech_input_locale_config_impl.h
diff --git a/ios/chrome/browser/voice/speech_input_locale_config_impl.h b/ios/chrome/browser/voice/speech_input_locale_config_impl.h
index bd942c13bf70d9b973b2b2d5445745e4ff8f4521..64b85928bf77d95986f62811e271d46c2b47aa8f 100644
--- a/ios/chrome/browser/voice/speech_input_locale_config_impl.h
+++ b/ios/chrome/browser/voice/speech_input_locale_config_impl.h
@@ -10,6 +10,8 @@
 #include "base/memory/singleton.h"
 #include "ios/chrome/browser/voice/speech_input_locale_config.h"
 
+class SpeechInputLocaleConfigImplTest;
+
 namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
@@ -61,6 +63,7 @@ class SpeechInputLocaleConfigImpl : public SpeechInputLocaleConfig {
   void InitializeTextToSpeechLangauges();
 
   friend struct base::DefaultSingletonTraits<SpeechInputLocaleConfigImpl>;
+  friend class ::SpeechInputLocaleConfigImplTest;
 
   // The list of available speech input locales.
   std::vector<SpeechInputLocale> available_locales_;