Implemented new Translate API for purely Objective-C clients.

ios/web_view/internal/translate/cwv_translation_controller_internal.h

+// 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.
+
+#ifndef IOS_WEB_VIEW_INTERNAL_TRANSLATE_CWV_TRANSLATION_CONTROLLER_INTERNAL_H
+#define IOS_WEB_VIEW_INTERNAL_TRANSLATE_CWV_TRANSLATION_CONTROLLER_INTERNAL_H
+
+#import "ios/web_view/public/cwv_translation_controller.h"
+
+#include "components/translate/core/browser/translate_step.h"
+#include "components/translate/core/common/translate_errors.h"
+#import "ios/web/public/web_state/web_state.h"
+#import "ios/web_view/internal/translate/web_view_translate_client.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+// Some internal methods needed to hide any C++ details.
+@interface CWVTranslationController ()

[Eugene But (OOO till 7-30), 2017/04/28 07:18:07]

nit: Should this be |CWVTranslationController (Internal)|?

[jzw1, 2017/04/28 09:55:33]

No. I believe we want it to be an extension since they are used to extend the
internal implementation, where as categories are used to add things not critical
to the internal implementation.
https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/Pr...
Also, I was following existing examples in ios/web_view.

+
+// Set to create a new translate stack under the new webState.
+@property(nonatomic, assign) web::WebState* webState;
+
+// Called to keep this class informed of the current translate progress.
+// |step| the state of current translation.
+// |sourceLanguage| the source language associated with the current |step|.
+// |targetLanguage| the target langauge associated with the current |step|.
+// |errorType| the error, if any for the current |step|.
+// |triggeredFromMenu| should be true if this was a result from user action.
+- (void)updateTranslateStep:(translate::TranslateStep)step
+             sourceLanguage:(const std::string&)sourceLanguage
+             targetLanguage:(const std::string&)targetLanguage
+                  errorType:(translate::TranslateErrors::Type)errorType
+          triggeredFromMenu:(bool)triggeredFromMenu;
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif  // IOS_WEB_VIEW_INTERNAL_TRANSLATE_CWV_TRANSLATION_CONTROLLER_INTERNAL_H