message: Document the files map in BuildBundler.
diff: @@ -30,6 +30,10 @@ export class BuildBundler extends Transform {
  private _buildAnalyzer: BuildAnalyzer;
  private _bundler: Bundler;
  + // A map of urls to file objects. As the transform stream handleds files
  + // coming into the stream, it collects all files here. After bundlling,
  + // we remove files from this set that have been inlined and replace
  + // entrypoint/fragment files with bundled versions.
  files = new Map<string, File>();
  constructor(config: ProjectConfig, buildAnalyzer: BuildAnalyzer) {
  