refactor(angular-material): apply requested changes

Author: SisIvanova

src/app/theming/angular/angular-sample.component.scss

@@ -67,7 +67,7 @@ $custom-mat-dark-theme: mat.define-dark-theme((
 ::ng-deep {
     @include mat.core();
 
-    .menu-theme {
+    .light-menu-theme {
         @include mat.menu-theme($custom-mat-light-theme);
     }
 

src/app/theming/angular/angular-sample.component.ts

@@ -17,7 +17,7 @@ export class AngularMaterialComponent implements OnInit {
     public dialog: IgxDialogComponent;
 
     @HostBinding('class')
-    public themesClass = 'light';
+    public themesClass: 'light' | 'dark' = 'light';
 
     firstFormGroup: FormGroup;
     secondFormGroup: FormGroup;
@@ -26,17 +26,32 @@ export class AngularMaterialComponent implements OnInit {
     private _dialogOverlaySettings2;
 
     constructor(private _formBuilder: FormBuilder, private overlayContainer: OverlayContainer) {
-        overlayContainer.getContainerElement().classList.add('menu-theme');
+        overlayContainer.getContainerElement().classList.add('light-menu-theme');
     }
 
     public lightTheme() {
         this.themesClass = 'light';
-        this.overlayContainer.getContainerElement().classList.remove('dark-menu-theme');
+        this.toggleOverlayClasses(this.themesClass);
     }
 
     public darkTheme() {
         this.themesClass = 'dark';
-        this.overlayContainer.getContainerElement().classList.add('dark-menu-theme');
+        this.toggleOverlayClasses(this.themesClass);
+    }
+
+    private toggleOverlayClasses(theme: 'light' | 'dark') {
+        const overlayClasses = this.overlayContainer.getContainerElement().classList;
+    
+        switch (theme) {
+            case 'light':
+                overlayClasses.remove('dark-menu-theme');
+                overlayClasses.add('light-menu-theme');
+                break;
+            case 'dark':
+                overlayClasses.remove('light-menu-theme');
+                overlayClasses.add('dark-menu-theme');
+                break;
+        }
     }
 
     public openDialog() {