anchor.diff:      bool updateExpectations = environment["updateExpectations"] == "true";
       bool updateComments = environment["updateComments"] == "true";
       bool skipVm = environment["skipVm"] == "true";
  +    String platformBinaries = environment["platformBinaries"];
  +    if (platformBinaries != null && !platformBinaries.endsWith('/')) {
  +      platformBinaries = '$platformBinaries/';
  +    }
       String astKindString = environment[AST_KIND_INDEX];
       AstKind astKind =
           astKindString == null ? null : AstKind.values[int.parse(astKindString)];
       return new FastaContext(
           vm,
           strongMode,
  +        platformBinaries == null
  +            ? computePlatformBinariesLocation()
  +            : Uri.base.resolve(platformBinaries),
           onlyCrashes,
           ignoreExpectations,
           updateExpectations,
  
positive.code:   final bool strongMode;
    final bool onlyCrashes;
    final Map<Program, KernelTarget> programToTarget = <Program, KernelTarget>{};
    Uri platformBinaries;
    Uri platformUri;
    Uri outlineUri;
    Program outline;
  
negative.code:   }
  
    Future ensurePlatformUris() async {
      if (platformUri == null) {
        platformUri = platformBinaries.resolve("vm_platform.dill");
        outlineUri = platformBinaries
            .resolve(strongMode ? "vm_outline_strong.dill" : "vm_outline.dill");
  