Expose way to enable/disable translate.

ios/web_view/public/cwv_translation_controller.h

Index: ios/web_view/public/cwv_translation_controller.h
diff --git a/ios/web_view/public/cwv_translation_controller.h b/ios/web_view/public/cwv_translation_controller.h
index 6e9476dece1f0a3c1cc285d61e2be1f9fc41a53c..f30113a3a9743f8de33b632e4f8f8051e8fd4c58 100644
--- a/ios/web_view/public/cwv_translation_controller.h
+++ b/ios/web_view/public/cwv_translation_controller.h
@@ -56,6 +56,10 @@ CWV_EXPORT
 // Only resets non-incognito settings.
 + (void)resetTranslationPolicies;
 
+// Enables or disables the translate feature. Only applies to non-incognito.

[Eugene But (OOO till 7-30), 2017/07/13 17:52:58]

Why does it work only for non-incognito? If I disable translation in app prefs,
as a user I would not want to see it in Incognito.

[jzw1, 2017/07/13 21:05:05]

Refactored so that the user can configure for both incognito and non-incognito.
This isn't perfect because incognito settings are only stored temporary in
memory and do not inherit any settings from non-incognito like Chrome does. If
we wanted to go that route, we would need to refactor our browser states some
more...

++ (BOOL)isTranslateEnabled;

[Hiroshi Ichikawa, 2017/07/13 07:28:59]

Optional: Maybe it can be just "isEnabled" because it's obvious that it's for
translate from the class it belongs to. Also, how about defining a @property for
this?

[Eugene But (OOO till 7-30), 2017/07/13 17:52:58]

Or isTranslationEnabled/setTranslationEnabled: to be consistent with
resetTranslationPolicies?

[jzw1, 2017/07/13 21:05:05]

I've renamed these in the new class CWVTranslationConfiguration.

++ (void)setTranslateEnabled:(BOOL)enabled;
+
 // Begins translation on the current page from |sourceLanguage| to
 // |targetLanguage|. These language parameters must be chosen from
 // |supportedLanguages|. Set |userInitiated| to YES if translation