Expose way to enable/disable translate.

ios/web_view/internal/cwv_preferences.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/cwv_preferences_internal.h"
+
+#include "components/prefs/pref_service.h"
+#include "components/translate/core/browser/translate_pref_names.h"
+#include "components/translate/core/browser/translate_prefs.h"
+#include "ios/web_view/internal/pref_names.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@implementation CWVPreferences {
+  PrefService* _prefService;
+}
+
+- (instancetype)initWithPrefService:(PrefService*)prefService {
+  self = [super init];
+  if (self) {
+    _prefService = prefService;
+  }
+  return self;
+}
+
+#pragma mark - Public Methods
+
+- (void)setTranslationEnabled:(BOOL)enabled {
+  _prefService->SetBoolean(prefs::kEnableTranslate, enabled);
+}
+
+- (BOOL)isTranslationEnabled {
+  return _prefService->GetBoolean(prefs::kEnableTranslate);
+}
+
+- (void)resetTranslationSettings {
+  translate::TranslatePrefs translatePrefs(
+      _prefService, prefs::kAcceptLanguages,
+      /*preferred_languages_pref=*/nullptr);
+  translatePrefs.ResetToDefaults();
+}
+
+@end