[ios] Fix changing source language bug in Translate

This change also removes unused delegate method implementations.

Fixed: 1035814
Change-Id: I2eff464a042b5a6917cad9da4e61daf8969672d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1986035Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728620}

ios/chrome/browser/ui/infobars/coordinators/infobar_translate_coordinator.mm

@@ -420,18 +420,6 @@ NSString* const kTranslateNotificationSnackbarCategory =
   // TODO(crbug.com/1014959): implement else logic. Should aything be done?
 }
 
-#pragma mark - InfobarTranslateLanguageSelectionDelegate
-
-- (void)didSelectSourceLanguageIndex:(int)languageIndex
-                            withName:(NSString*)languageName {
-  // TODO(crbug.com/1014959): Implement.
-}
-
-- (void)didSelectTargetLanguageIndex:(int)languageIndex
-                            withName:(NSString*)languageName {
-  // TODO(crbug.com/1014959): Implement.
-}
-
 #pragma mark - Private
 
 // Helper method for performInfobarAction, which also allows for

ios/chrome/browser/ui/infobars/coordinators/infobar_translate_mediator.mm

@@ -186,9 +186,9 @@ const int kInvalidLanguageIndex = -1;
 
   base::string16 targetLanguage =
       self.translateInfobarDelegate->target_language_name();
-  if (self.newSourceLanguageIndex != kInvalidLanguageIndex) {
+  if (self.newTargetLanguageIndex != kInvalidLanguageIndex) {
     targetLanguage = self.translateInfobarDelegate->language_name_at(
-        self.newSourceLanguageIndex);
+        self.newTargetLanguageIndex);
   }
   [self.modalConsumer
       setupModalViewControllerWithPrefs: