extensions/typescript-language-features/src/utils/managedFileContext.ts/ManagedFileContextManager/onDidChangeActiveTextEditor
class ManagedFileContextManager:	private onDidChangeActiveTextEditor(editor?: vscode.TextEditor): void {
		if (editor) {
			this.updateContext(this.isManagedFile(editor));
		} else {
			this.updateContext(false);
		}
	}