src/vs/workbench/services/search/node/fileSearch.ts/Engine/search
class Engine:	search(onResult: (result: IRawFileMatch) => void, onProgress: (progress: IProgressMessage) => void, done: (error: Error | null, complete: ISearchEngineSuccess) => void): void {
		this.walker.walk(this.folderQueries, this.extraFiles, onResult, onProgress, (err: Error | null, isLimitHit: boolean) => {
			done(err, {
				limitHit: isLimitHit,
				stats: this.walker.getStats(),
				messages: [],
			});
		});
	}