[infra] Support different local named configurations in tools/test.dart.

This change lets one download the results for one named configuration but do
the local testing with another named configuration. This change addresses
the issue of developers needing to do local testing where there is no
builder matching their local environment. This allows e.g. a dart2js
developer on Windows to use the results for the Linux variant of the same
named configuration, which should be identical or close enough for the
comparison to be meaningful.

Fixes https://github.com/dart-lang/sdk/issues/36151

Change-Id: I1a387a9767cdf5ba99964535478201c0142f15e1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/96102
Reviewed-by: William Hesse <whesse@google.com>

tools/test.dart

@@ -281,6 +281,11 @@ void main(List<String> args) async {
       abbr: "n",
       help: "The named test configuration that supplies the\nvalues for all "
           "test options, specifying how tests\nshould be run.");
+  parser.addOption("local-configuration",
+      abbr: "N",
+      help: "Use a different named configuration for local\ntesting than the "
+          "named configuration the baseline\nresults were downloaded for.\nThe"
+          "results may be inexact if the baseline configuration is different.");
   parser.addOption("remote",
       abbr: "R",
       help: "Compare with this remote and git branch",
@@ -351,9 +356,16 @@ ${parser.usage}""");
     return;
   }
   final namedConfiguration = namedConfigurations.single;
+  final localConfiguration =
+      options["local-configuration"] ?? namedConfiguration;
   for (final builder in builders) {
-    print("Testing the named configuration $namedConfiguration "
-        "compared with builder $builder");
+    if (localConfiguration != namedConfiguration) {
+      print("Testing the named configuration $localConfiguration "
+          "compared with builder $builder's configuration $namedConfiguration");
+    } else {
+      print("Testing the named configuration $localConfiguration "
+          "compared with builder $builder");
+    }
   }
 
   // Find out where the current HEAD branched.
@@ -391,16 +403,31 @@ ${parser.usage}""");
 
     // Write out the merged results for the builders.
     if (2 <= builders.length) {
-      print("Merging downloaded results from the builders...");
       await new File("${outDirectory.path}/previous.json").writeAsString(
           mergedResults.values.map((data) => jsonEncode(data) + "\n").join(""));
       await new File("${outDirectory.path}/flaky.json").writeAsString(
           mergedFlaky.values.map((data) => jsonEncode(data) + "\n").join(""));
     }
 
+    // Override the named configuration in the baseline data if needed.
+    if (namedConfiguration != localConfiguration) {
+      for (final path in [
+        "${outDirectory.path}/previous.json",
+        "${outDirectory.path}/flaky.json"
+      ]) {
+        final results = await loadResultsMap(path);
+        final records = results.values
+            .where((r) => r["configuration"] == namedConfiguration)
+            .toList()
+              ..forEach((r) => r["configuration"] = localConfiguration);
+        await new File(path).writeAsString(
+            records.map((data) => jsonEncode(data) + "\n").join(""));
+      }
+    }
+
     // Run the tests.
     final arguments = [
-      "--named-configuration=$namedConfiguration",
+      "--named-configuration=$localConfiguration",
       "--output-directory=${outDirectory.path}",
       "--clean-exit",
       "--silent-failures",
@@ -438,7 +465,7 @@ ${parser.usage}""");
       final deflakeDirectory = new Directory("${outDirectory.path}/$i");
       await deflakeDirectory.create();
       final deflakeArguments = <String>[
-        "--named-configuration=$namedConfiguration",
+        "--named-configuration=$localConfiguration",
         "--output-directory=${deflakeDirectory.path}",
         "--clean-exit",
         "--silent-failures",