Expose way to enable/disable translate.

ios/web_view/internal/cwv_web_view_configuration.mm

Index: ios/web_view/internal/cwv_web_view_configuration.mm
diff --git a/ios/web_view/internal/cwv_web_view_configuration.mm b/ios/web_view/internal/cwv_web_view_configuration.mm
index 736dfbbd3fafcc0810b8aa849780bd4b3c28a064..36696713c8450143e8b95afe5818f9c3f4d719d1 100644
--- a/ios/web_view/internal/cwv_web_view_configuration.mm
+++ b/ios/web_view/internal/cwv_web_view_configuration.mm
@@ -8,6 +8,7 @@
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_restrictions.h"
 #include "ios/web_view/internal/app/application_context.h"
+#import "ios/web_view/internal/cwv_preferences_internal.h"
 #import "ios/web_view/internal/cwv_user_content_controller_internal.h"
 #include "ios/web_view/internal/web_view_browser_state.h"
 #include "ios/web_view/internal/web_view_global_state_util.h"
@@ -28,6 +29,7 @@
 
 @implementation CWVWebViewConfiguration
 
+@synthesize preferences = _preferences;
 @synthesize userContentController = _userContentController;
 
 + (instancetype)defaultConfiguration {
@@ -68,6 +70,9 @@
   if (self) {
     _browserState = std::move(browserState);
 
+    _preferences =
+        [[CWVPreferences alloc] initWithPrefService:_browserState->GetPrefs()];
+
     _userContentController =
         [[CWVUserContentController alloc] initWithConfiguration:self];
   }