Implemented new Translate API for purely Objective-C clients.

ios/web_view/public/cwv_translation_controller.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_PUBLIC_CWV_TRANSLATION_CONTROLLER_H
+#define IOS_WEB_VIEW_PUBLIC_CWV_TRANSLATION_CONTROLLER_H
+
+#import <ChromeWebView/cwv_export.h>
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@class CWVTranslationController;
+@class CWVLanguageDetectionResult;
+@class CWVTranslationLanguage;
+
+// The error domain for translation errors.
+extern NSErrorDomain const CWVTranslationErrorDomain;
+
+// Possible error codes during translation.
+// No connectivity.
+extern const NSInteger CWVTranslationErrorNetwork;
+// The translation script failed to initialize.
+extern const NSInteger CWVTranslationErrorInitializationError;
+// The page's language could not be detected.
+extern const NSInteger CWVTranslationErrorUnknownLanguage;
+// The server detected a language that the browser does not know.
+extern const NSInteger CWVTranslationErrorUnsupportedLanguage;
+// The original and target languages are the same.
+extern const NSInteger CWVTranslationErrorIdenticalLanguages;
+// An error was reported by the translation script during translation.
+extern const NSInteger CWVTranslationErrorTranslationError;
+// The library doesn't finish the translation.
+extern const NSInteger CWVTranslationErrorTranslationTimeout;
+// The library raises an unexpected exception.
+extern const NSInteger CWVTranslationErrorUnexpectedScriptError;
+// The library is blocked because of bad origin.
+extern const NSInteger CWVTranslationErrorBadOrigin;
+// Loader fails to load a dependent JavaScript.
+extern const NSInteger CWVTranslationErrorScriptLoadError;
+
+// Updates delegate on translation progress.
+CWV_EXPORT
+@protocol CWVTranslationControllerDelegate<NSObject>

[michaeldo, 2017/05/01 18:25:38]

Please move delegate definition to it's own file.

Ref:
https://chromium.googlesource.com/chromium/src/+/master/styleguide/c++/c++.md...

[jzw1, 2017/05/08 03:36:28]

Done.

+@optional
+// Called when language detection is completed. Contains information on the
+// detected language, the assumed target language for translation, as well as
+// all languages supported by this translation controller.
+// |error| will be filled if language detection failed.

[michaeldo, 2017/05/01 18:25:38]

s/filled/nonnull

[jzw1, 2017/05/08 03:36:28]

Done.

+- (void)translationController:(CWVTranslationController*)controller
+    didFinishLanguageDetectionWithResult:(CWVLanguageDetectionResult*)result

[michaeldo, 2017/05/01 18:25:37]

I think didFinishLanguageDetectionWithResult should be required, because below
comment on translatePageFromLanguage:toLanguage: states the client can't call
that method until after receiving this method.

[jzw1, 2017/05/08 03:36:28]

That's fair.

+                                   error:(nullable NSError*)error;
+
+// Called when a translation has started.
+- (void)translationController:(CWVTranslationController*)controller
+    didStartTranslationFromLanguage:(CWVTranslationLanguage*)sourceLanguage
+                         toLanguage:(CWVTranslationLanguage*)targetLanguage;
+
+// Called when translation finishes. |error| will be filled if it failed.

[michaeldo, 2017/05/01 18:25:38]

s/filled/nonnull

[jzw1, 2017/05/08 03:36:28]

Done.

+- (void)translationController:(CWVTranslationController*)controller
+    didFinishTranslationFromLanguage:(CWVTranslationLanguage*)sourceLanguage
+                          toLanguage:(CWVTranslationLanguage*)targetLanguage
+                               error:(nullable NSError*)error;
+
+@end
+
+// Main interface for access to translation features.

[michaeldo, 2017/05/01 18:25:38]

"Main interface" sounds like there are other non-main interfaces. What about
simplifying all 3 lines of comment to just this line:

// Allows page translation from one language to another.

The revert ability and the delegate can be clearly seen from the header methods
so I don't think we need to explain in the comments.

[jzw1, 2017/05/08 03:36:28]

Fine by me.

+// Allows page translation from one language to another, and to revert it.
+// Provides delegate to inform translation progress.
+CWV_EXPORT
+@interface CWVTranslationController : NSObject
+
+// Delegate to receive translation callbacks.
+@property(nullable, nonatomic, weak) id<CWVTranslationControllerDelegate>
+    delegate;
+
+// Begins translation on the current page from |sourceLanguage| to
+// |targetLanguage|. These language parameters must be chosen from
+// a CWWLanguageDetectionResult's |supportedLanguages|.
+// This must not be called before the |delegate| receives
+// |translationController:didFinishLanguageDetectionWithResult:error:|.
+// TODO(crbug.com/706289): Document what happens if you call this out of order
+// or many times.
+- (void)translatePageFromLanguage:(CWVTranslationLanguage*)sourceLanguage
+                       toLanguage:(CWVTranslationLanguage*)targetLanguage;
+
+// Reverts any translations done back to the original page language.
+// Note that the original page language  may be different from |sourceLanguage|
+// passed to |translatePageFromLanguage:toLanguage:| above.
+// This must not be called before the |delegate| receives
+// |translationController:didFinishLanguageDetectionWithResult:error:|.
+// TODO(crbug.com/706289): Document what happens if you call this out of order.
+- (void)revertTranslation;
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+#endif  // IOS_WEB_VIEW_PUBLIC_CWV_TRANSLATION_CONTROLLER_H