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

The browser process sends the system spellchecker language to the
renderer to initialize its text breaker. The text breaker is used when
providing suggestions in the context menu. If the text breaker is not
initialized, the menu has no suggestions.

The browser saves the system spellchecker language into the unsynced
preference prefs::kSpellCheckDictionaries. This preference is also used
by the spelling service client. If the preference is empty, then the
client is disabled.

BUG=577835

Review URL: https://codereview.chromium.org/1602303002

Cr-Commit-Position: refs/heads/master@{#371605}

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();
 

chrome/browser/spellchecker/spellcheck_platform_android.cc

@@ -13,6 +13,10 @@ namespace spellcheck_platform {
 void GetAvailableLanguages(std::vector<std::string>* spellcheck_languages) {
 }
 
+std::string GetSpellCheckerLanguage() {
+  return std::string();
+}
+
 bool SpellCheckerAvailable() {
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kEnableAndroidSpellChecker);

chrome/browser/spellchecker/spellcheck_platform_mac.mm

@@ -109,6 +109,10 @@ void GetAvailableLanguages(std::vector<std::string>* spellcheck_languages) {
   }
 }
 
+std::string GetSpellCheckerLanguage() {
+  return ConvertLanguageCodeFromMac([SharedSpellChecker() language]);
+}
+
 bool SpellCheckerAvailable() {
   // If this file was compiled, then we know that we are on OS X 10.5 at least
   // and can safely return true here.

chrome/browser/spellchecker/spellcheck_service.cc

@@ -48,15 +48,27 @@ SpellcheckService::SpellcheckService(content::BrowserContext* context)
   StringListPrefMember dictionaries_pref;
   dictionaries_pref.Init(prefs::kSpellCheckDictionaries, prefs);
   std::string first_of_dictionaries;
-  if (!dictionaries_pref.GetValue().empty())
-    first_of_dictionaries = dictionaries_pref.GetValue().front();
 
-  // For preference migration, set the new preference kSpellCheckDictionaries
-  // to be the same as the old kSpellCheckDictionary.
+#if defined(USE_BROWSER_SPELLCHECKER)
+  // Ensure that the renderer always knows the platform spellchecking language.
+  // This language is used for initialization of the text iterator. If the
+  // iterator is not initialized, then the context menu does not show spellcheck
+  // suggestions.
+  //
+  // No migration is necessary, because the spellcheck language preference is
+  // not user visible or modifiable in Chrome on Mac.
+  dictionaries_pref.SetValue(std::vector<std::string>(
+      1, spellcheck_platform::GetSpellCheckerLanguage()));
+  first_of_dictionaries = dictionaries_pref.GetValue().front();
+#else
+  // Migrate preferences from single-language to multi-language schema.
   StringPrefMember single_dictionary_pref;
   single_dictionary_pref.Init(prefs::kSpellCheckDictionary, prefs);
   std::string single_dictionary = single_dictionary_pref.GetValue();
 
+  if (!dictionaries_pref.GetValue().empty())
+    first_of_dictionaries = dictionaries_pref.GetValue().front();
+
   if (first_of_dictionaries.empty() && !single_dictionary.empty()) {
     first_of_dictionaries = single_dictionary;
     dictionaries_pref.SetValue(
@@ -67,6 +79,8 @@ SpellcheckService::SpellcheckService(content::BrowserContext* context)
 
   // If a user goes from single language to multi-language spellchecking with
   // spellchecking disabled the dictionaries preference should be blanked.
+  // TODO(krb): Remove this block of code when allowing to disable multi-lingual
+  // spellcheck.
   if (!prefs->GetBoolean(prefs::kEnableContinuousSpellcheck) &&
       chrome::spellcheck_common::IsMultilingualSpellcheckEnabled()) {
     dictionaries_pref.SetValue(std::vector<std::string>());
@@ -75,11 +89,14 @@ SpellcheckService::SpellcheckService(content::BrowserContext* context)
 
   // If a user goes back to single language spellchecking make sure there is
   // only one language in the dictionaries preference.
+  // TODO(krb): Remove this block of code when disabling single-language
+  // spellcheck.
   if (!chrome::spellcheck_common::IsMultilingualSpellcheckEnabled() &&
       dictionaries_pref.GetValue().size() > 1) {
     dictionaries_pref.SetValue(
         std::vector<std::string>(1, first_of_dictionaries));
   }
+#endif  // defined(USE_BROWSER_SPELLCHECKER)
 
   std::string language_code;
   std::string country_code;