Use type-safe events for FileManager

Bug: 1228674
Change-Id: I9daa26f61f0cbd65cc5ba07f09d2c0e2b39158c3
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/3081724
Reviewed-by: Sigurd Schneider <[email protected]>
Commit-Queue: Kateryna Prokopenko <[email protected]>
diff --git a/front_end/models/bindings/FileUtils.ts b/front_end/models/bindings/FileUtils.ts
index 589c4c5..8e64124 100644
--- a/front_end/models/bindings/FileUtils.ts
+++ b/front_end/models/bindings/FileUtils.ts
@@ -245,7 +245,7 @@
     Workspace.FileManager.FileManager.instance().close(this.fileName);
   }
 
-  private onAppendDone(event: Common.EventTarget.EventTargetEvent): void {
+  private onAppendDone(event: Common.EventTarget.EventTargetEvent<string>): void {
     if (event.data !== this.fileName) {
       return;
     }