Add support for $i18n{} localized strings to ios/web.

ios/web/public/web_ui_ios_data_source.h

Index: ios/web/public/web_ui_ios_data_source.h
diff --git a/ios/web/public/web_ui_ios_data_source.h b/ios/web/public/web_ui_ios_data_source.h
index 8feebb25b1f7ecff82d0057abb92707975ac3639..edfcd8ab521e8cad651a83a8583b72fd4ba165a0 100644
--- a/ios/web/public/web_ui_ios_data_source.h
+++ b/ios/web/public/web_ui_ios_data_source.h
@@ -9,6 +9,10 @@
 #include "base/strings/string16.h"
 #include "base/supports_user_data.h"
 
+namespace base {
+class DictionaryValue;
+}
+
 namespace web {
 class BrowserState;
 
@@ -34,6 +38,9 @@ class WebUIIOSDataSource : public base::SupportsUserData {
   // dictionary.
   virtual void AddLocalizedString(const std::string& name, int ids) = 0;
 
+  virtual void AddLocalizedStrings(
+      const base::DictionaryValue& localized_strings) = 0;
+
   // Adds a boolean keyed to its name to our dictionary.
   virtual void AddBoolean(const std::string& name, bool value) = 0;