[Snackbar] Add messageAnimationEnabled to control the animation behav…

…ior of snackbar.

PiperOrigin-RevId: 591368769

components/Snackbar/src/MDCSnackbarManager.h

@@ -369,6 +369,13 @@ NS_ASSUME_NONNULL_END
  */
 @property(nonatomic, assign) BOOL shouldShowMessageWhenVoiceOverIsRunning;
 
+/**
+ If disabled, @c MDCSnackbarManager will not show or dismiss snackbar messages with animation.
+
+ Default is set to YES.
+ */
+@property(nonatomic, assign, getter=isMessageAnimationEnabled) BOOL messageAnimationEnabled;
+
 /**
  The delegate for MDCSnackbarManager.defaultManager through which it may inform of snackbar
  presentation updates.

components/Snackbar/src/MDCSnackbarManager.m

@@ -264,7 +264,7 @@ - (void)displaySnackbarViewForMessage:(MDCSnackbarMessage *)message {
   // only if the user isn't running VoiceOver.
   [self.overlayView
       showSnackbarView:snackbarView
-              animated:YES
+              animated:self.manager.isMessageAnimationEnabled
             completion:^{
               if ([self snackbarAllowsFocus:snackbarView]) {
                 UIAccessibilityPostNotification(self.manager.focusAccessibilityNotification,
@@ -336,7 +336,7 @@ - (void)hideSnackbarViewReally:(MDCSnackbarMessageView *)snackbarView
   }
 
   [self.overlayView
-      dismissSnackbarViewAnimated:YES
+      dismissSnackbarViewAnimated:self.manager.isMessageAnimationEnabled
                        completion:^{
                          self.overlayView.hidden = YES;
                          [self deactivateOverlay:self.overlayView];
@@ -634,6 +634,7 @@ - (instancetype)initWithWindowScene:(nullable UIWindowScene *)windowScene {
     _mdc_overrideBaseElevation = -1;
     _focusAccessibilityNotification = UIAccessibilityLayoutChangedNotification;
     _shouldShowMessageWhenVoiceOverIsRunning = YES;
+    _messageAnimationEnabled = YES;
     _enableDismissalAccessibilityAffordance = NO;
     _usesGM3Shapes = NO;
   }