anchor.diff:  class KernelCompiler {
     const KernelCompiler();
   
  -  Future<CompilerOutput> compile(
  -    {String sdkRoot,
  +  Future<CompilerOutput> compile({
  +    String sdkRoot,
       String mainPath,
       String outputFilePath,
       String depFilePath,
  
positive.code:     String incrementalCompilerByteStorePath,
      String packagesPath,
      List<String> fileSystemRoots,
      String fileSystemScheme}) async {
      final String frontendServer = artifacts.getArtifactPath(
        Artifact.frontendServerSnapshotForEngineDartSdk
      );
  
negative.code: typedef void CompilerMessageConsumer(String message);
  
  class CompilerOutput {
    final String outputFilename;
    final int errorCount;
  
    const CompilerOutput(this.outputFilename, this.errorCount);
  }
  
  class _StdoutHandler {
  