Add `noImplicitOverride`

`noImplicitOverride` guarantees type safety when overriding a class method. This also improves refactoring behavior.

The primary motivation for `noImplicitOverride` is for using with Lit elements where overriding methods is important.

Bug: 1402569
Change-Id: Ia095c38a6d1fc160f9b08c350d6f7248daab38a4
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/4443322
Reviewed-by: Jack Franklin <[email protected]>
Commit-Queue: Randolf Jung <[email protected]>
diff --git a/front_end/panels/elements/ClassesPaneWidget.ts b/front_end/panels/elements/ClassesPaneWidget.ts
index e1db5c7..3fa82d3 100644
--- a/front_end/panels/elements/ClassesPaneWidget.ts
+++ b/front_end/panels/elements/ClassesPaneWidget.ts
@@ -149,7 +149,7 @@
     this.update();
   }
 
-  wasShown(): void {
+  override wasShown(): void {
     super.wasShown();
     this.update();
     this.registerCSSFiles([classesPaneWidgetStyles]);