[iOS] Migrate MDCSnackbarManager to defaultManager in Chrome.

TBR=marq@chromium.org

This fixes a BUILD issue due to a deprecated API in MDCSnackbarManager.

Bug: 1117399
Change-Id: I27a9c5ce03e319bb4f402236d32f593a4d7f073e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2367032Reviewed-by: Nohemi Fernandez <fernandex@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Nohemi Fernandez <fernandex@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800084}

ios/chrome/browser/ui/bookmarks/bookmark_interaction_controller.mm

@@ -386,8 +386,9 @@ enum class PresentedState {
 
 - (void)dismissSnackbar {
   // Dismiss any bookmark related snackbar this controller could have presented.
-  [MDCSnackbarManager dismissAndCallCompletionBlocksWithCategory:
-                          bookmark_utils_ios::kBookmarksSnackbarCategory];
+  [[MDCSnackbarManager defaultManager]
+      dismissAndCallCompletionBlocksWithCategory:
+          bookmark_utils_ios::kBookmarksSnackbarCategory];
 }
 
 #pragma mark - BookmarkEditViewControllerDelegate

ios/chrome/browser/ui/settings/password/passwords_settings_app_interface.mm

@@ -162,7 +162,7 @@ static MockReauthenticationModule* _mockReauthenticationModule;
 }
 
 + (void)dismissSnackBar {
-  [MDCSnackbarManager
+  [[MDCSnackbarManager defaultManager]
       dismissAndCallCompletionBlocksWithCategory:@"PasswordsSnackbarCategory"];
 }
 

ios/chrome/browser/ui/translate/translate_notification_presenter.mm

@@ -99,8 +99,9 @@ NSString* const kTranslateNotificationSnackbarCategory =
 }
 
 - (void)dismissNotification {
-  [MDCSnackbarManager dismissAndCallCompletionBlocksWithCategory:
-                          kTranslateNotificationSnackbarCategory];
+  [[MDCSnackbarManager defaultManager]
+      dismissAndCallCompletionBlocksWithCategory:
+          kTranslateNotificationSnackbarCategory];
 }
 
 #pragma mark - Private