Implemented new Translate API for purely Objective-C clients.

ios/web_view/internal/cwv_web_view.mm

Index: ios/web_view/internal/cwv_web_view.mm
diff --git a/ios/web_view/internal/cwv_web_view.mm b/ios/web_view/internal/cwv_web_view.mm
index 503cadd517ccbf86bb37f8a44104ccd04d337d73..ede3291bb1b3ff6f4e3de9554ce4b70ff1e2de0e 100644
--- a/ios/web_view/internal/cwv_web_view.mm
+++ b/ios/web_view/internal/cwv_web_view.mm
@@ -23,6 +23,7 @@
 #import "ios/web_view/internal/cwv_html_element_internal.h"
 #import "ios/web_view/internal/cwv_navigation_action_internal.h"
 #import "ios/web_view/internal/cwv_web_view_configuration_internal.h"
+#import "ios/web_view/internal/translate/cwv_translation_controller_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/internal/web_view_java_script_dialog_presenter.h"
@@ -82,9 +83,9 @@ static NSString* gUserAgentProduct = nil;
 
 @synthesize configuration = _configuration;
 @synthesize navigationDelegate = _navigationDelegate;
-@synthesize translationDelegate = _translationDelegate;
 @synthesize estimatedProgress = _estimatedProgress;
 @synthesize UIDelegate = _UIDelegate;
+@synthesize translationController = _translationController;
 
 + (NSString*)userAgentProduct {
   return gUserAgentProduct;
@@ -187,12 +188,6 @@ static NSString* gUserAgentProduct = nil;
   _javaScriptDialogPresenter->SetUIDelegate(_UIDelegate);
 }
 
-- (void)setTranslationDelegate:(id<CWVTranslateDelegate>)translationDelegate {
-  _translationDelegate = translationDelegate;
-  ios_web_view::WebViewTranslateClient::FromWebState(_webState.get())
-      ->set_translate_delegate(translationDelegate);
-}
-
 // -----------------------------------------------------------------------
 // WebStateObserver implementation.
 
@@ -290,6 +285,20 @@ static NSString* gUserAgentProduct = nil;
   return _javaScriptDialogPresenter.get();
 }
 
+#pragma mark - Translation
+
+- (CWVTranslationController*)translationController {

[Hiroshi Ichikawa, 2017/04/26 08:40:57]

When -resetWebStateWithSessionStorage: is called after the first call to
-translationController, I believe you need to update _translationController with
the new _webState.

FYI You may do something similar to my CL:
https://codereview.chromium.org/2842953002/

[jzw1, 2017/04/27 04:54:01]

Are you OK if i just nil it out _translationController inside resetWebState?

[Hiroshi Ichikawa, 2017/04/27 05:35:42]

I believe it doesn't work. Two cases:

1. The user stores |translationController| to a variable before -resetWebState
is called. Then the controller keeps referring to the old WebState.

2. The user assigns a delegate to |translationController| before -resetWebState
is called. Then the delegate won't be called after -resetWebState because the
delegate is not inherited to the new |translationController|.

One solution I can think of is to allow reassigning
CWVTranslationController.translateClient and reassign it in -resetWebState as I
do in:
https://codereview.chromium.org/2842953002/

[jzw1, 2017/04/27 07:03:18]

What if I just set a webState on translationController?

[Hiroshi Ichikawa, 2017/04/27 07:17:22]

Yeah it looks calling -[CWVTranslationController setWebState:] on -resetWebState
should work. Looks like -setWebState: already does the required job.

+  if (!_translationController) {
+    // Initialize Translate.
+    ios_web_view::WebViewTranslateClient::CreateForWebState(_webState.get());
+    ios_web_view::WebViewTranslateClient* translateClient =
+        ios_web_view::WebViewTranslateClient::FromWebState(_webState.get());
+    _translationController = [[CWVTranslationController alloc]
+        initWithWebViewTranslateClient:translateClient];
+  }
+  return _translationController;
+}
+
 #pragma mark - Preserving and Restoring State
 
 - (void)encodeRestorableStateWithCoder:(NSCoder*)coder {
@@ -341,9 +350,6 @@ static NSString* gUserAgentProduct = nil;
       base::MakeUnique<ios_web_view::WebViewJavaScriptDialogPresenter>(self,
                                                                        nullptr);
 
-  // Initialize Translate.
-  ios_web_view::WebViewTranslateClient::CreateForWebState(_webState.get());
-
   [self addInternalWebViewAsSubview];
 }