[ios] Mark Translate Message as high priority after a Translate

This change caters to users that have a tendency to toggle between
a different language and the original language of a page.

Bug: 1014959, 1042410
Change-Id: I718124ce7791762f7311e511e2cac6d5d7d5a671
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2003252
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Auto-Submit: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732395}

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

@@ -128,6 +128,13 @@ NSString* const kTranslateNotificationSnackbarCategory =
       break;
     case translate::TranslateStep::TRANSLATE_STEP_AFTER_TRANSLATE: {
       self.displayShowOriginalBanner = YES;
+      // Once the user asks for the page to be translated once, always make the
+      // banner presentation high priority even if the user requests to show the
+      // original language, since there is a possibility the user will be
+      // toggling between languages. In addition, reverting an infobar does not
+      // show the "Translate?" banner, so every subsequent banner presentation
+      // will be a "Show Original" one.
+      self.highPriorityPresentation = YES;
       [self.badgeDelegate infobarWasAccepted:self.infobarType
                                  forWebState:self.webState];