Expose method to reset translate settings.

ios/web_view/internal/translate/cwv_translation_controller.mm

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web_view/internal/translate/cwv_translation_controller_internal.h"
 
 #include <string>
 
 #include "base/memory/ptr_util.h"
 #include "base/strings/string16.h"
 #include "base/strings/sys_string_conversions.h"
 #include "components/translate/core/browser/translate_download_manager.h"
 #include "components/translate/core/browser/translate_manager.h"
+#import "ios/web_view/internal/cwv_web_view_configuration_internal.h"
+#include "ios/web_view/internal/pref_names.h"
 #import "ios/web_view/internal/translate/cwv_translation_language_internal.h"
 #import "ios/web_view/internal/translate/web_view_translate_client.h"
+#include "ios/web_view/internal/web_view_browser_state.h"
 #import "ios/web_view/public/cwv_translation_controller_delegate.h"
 #import "ios/web_view/public/cwv_translation_policy.h"
 #include "ui/base/l10n/l10n_util.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 NSErrorDomain const CWVTranslationErrorDomain =
     @"org.chromium.chromewebview.TranslationErrorDomain";
@@ skipping 32 matching lines @@
 
 @implementation CWVTranslationController {
   ios_web_view::WebViewTranslateClient* _translateClient;
   std::unique_ptr<translate::TranslatePrefs> _translatePrefs;
 }
 
 @synthesize delegate = _delegate;
 @synthesize supportedLanguagesByCode = _supportedLanguagesByCode;
 @synthesize webState = _webState;
 
+#pragma mark - Class Methods
+
++ (void)resetTranslationPolicies {
+  ios_web_view::WebViewBrowserState* browserState =
+      [CWVWebViewConfiguration defaultConfiguration].browserState;

[michaeldo, 2017/07/07 18:16:01]

Sorry I didn't think of this before, but will this apply to other already
created and in use configurations? If not, we should explain in the method
comment that is will only apply to configurations created after it is called.

[Eugene But (OOO till 7-30), 2017/07/07 20:10:28]

What if clients want to reset policies for incognito configuration? Would it be
better to make |resetTranslationPolicies| instance method and pass prefs object
to TranslationController init?

[jzw1, 2017/07/08 01:09:41]

OK guys I've changed it so:
1. global instance for incognito and non-incognito browse states (2 total).
2. incognito browse state uses in memory store. 

this means translate preferences are not shared between incognito and
non-incognito.

[Eugene But (OOO till 7-30), 2017/07/10 16:17:43]

All methods related to translate policies are instance methods. Is there a
reason why only |reset| method is a class method? This looks inconsistent to me.

[jzw1, 2017/07/10 18:51:40]

The reason is because you can't get to an instance of CWVTranslationController
without having a CWVWebView, but you should still be able to clear translate
preferences without any existing CWVWebView. 

+  translate::TranslatePrefs translatePrefs(browserState->GetPrefs(),
+                                           prefs::kAcceptLanguages, nullptr);
+  translatePrefs.ResetToDefaults();
+}
+
 #pragma mark - Internal Methods
 
 - (void)setWebState:(web::WebState*)webState {
   _webState = webState;
 
   ios_web_view::WebViewTranslateClient::CreateForWebState(_webState);
   _translateClient =
       ios_web_view::WebViewTranslateClient::FromWebState(_webState);
   _translateClient->set_translation_controller(self);
   _translatePrefs = _translateClient->translate_manager()
@@ skipping 176 matching lines @@
   }
   return _supportedLanguagesByCode;
 }
 
 - (CWVTranslationLanguage*)languageWithCode:(const std::string&)languageCode {
   NSString* languageCodeString = base::SysUTF8ToNSString(languageCode);
   return self.supportedLanguagesByCode[languageCodeString];
 }
 
 @end