Add support for --dart2js-path and --dart2js-args.

lib/src/runner/configuration.dart

Index: lib/src/runner/configuration.dart
diff --git a/lib/src/runner/configuration.dart b/lib/src/runner/configuration.dart
index c7dbb574c4992700c51b0a6fa230ab6187de116d..4587641ed0ca320a7dd2aff93b8295307afb8901 100644
--- a/lib/src/runner/configuration.dart
+++ b/lib/src/runner/configuration.dart
@@ -69,6 +69,13 @@ class Configuration {
   String get packageRoot => _packageRoot ?? p.join(p.current, 'packages');
   final String _packageRoot;
 
+  /// The path to dart2js.
+  String get dart2jsPath => _dart2jsPath ?? p.join(sdkDir, 'bin', 'dart2js');
+  final String _dart2jsPath;
+
+  /// Additional arguments to pass to dart2js.
+  final List<String> dart2jsArgs;
+
   /// The name of the reporter to use to display results.
   String get reporter => _reporter ?? defaultReporter;
   final String _reporter;
@@ -267,6 +274,8 @@ class Configuration {
       bool pauseAfterLoad,
       bool color,
       String packageRoot,
+      String dart2jsPath,
+      Iterable<String> dart2jsArgs,
       String reporter,
       int pubServePort,
       int concurrency,
@@ -295,6 +304,8 @@ class Configuration {
         pauseAfterLoad: pauseAfterLoad,
         color: color,
         packageRoot: packageRoot,
+        dart2jsPath: dart2jsPath,
+        dart2jsArgs: dart2jsArgs,
         reporter: reporter,
         pubServePort: pubServePort,
         concurrency: concurrency,
@@ -362,6 +373,8 @@ class Configuration {
           bool pauseAfterLoad,
           bool color,
           String packageRoot,
+          String dart2jsPath,
+          Iterable<String> dart2jsArgs,
           String reporter,
           int pubServePort,
           int concurrency,
@@ -388,6 +401,8 @@ class Configuration {
         _pauseAfterLoad = pauseAfterLoad,
         _color = color,
         _packageRoot = packageRoot,
+        _dart2jsPath = dart2jsPath,
+        dart2jsArgs = dart2jsArgs?.toList() ?? [],
         _reporter = reporter,
         pubServeUrl = pubServePort == null
             ? null
@@ -460,6 +475,8 @@ class Configuration {
         pauseAfterLoad: other._pauseAfterLoad ?? _pauseAfterLoad,
         color: other._color ?? _color,
         packageRoot: other._packageRoot ?? _packageRoot,
+        dart2jsPath: other._dart2jsPath ?? _dart2jsPath,
+        dart2jsArgs: dart2jsArgs.toList()..addAll(other.dart2jsArgs),
         reporter: other._reporter ?? _reporter,
         pubServePort: (other.pubServeUrl ?? pubServeUrl)?.port,
         concurrency: other._concurrency ?? _concurrency,
@@ -499,6 +516,8 @@ class Configuration {
       bool pauseAfterLoad,
       bool color,
       String packageRoot,
+      String dart2jsPath,
+      Iterable<String> dart2jsArgs,
       String reporter,
       int pubServePort,
       int concurrency,
@@ -527,6 +546,8 @@ class Configuration {
         pauseAfterLoad: pauseAfterLoad ?? _pauseAfterLoad,
         color: color ?? _color,
         packageRoot: packageRoot ?? _packageRoot,
+        dart2jsPath: dart2jsPath ?? _dart2jsPath,
+        dart2jsArgs: dart2jsArgs?.toList() ?? this.dart2jsArgs,
         reporter: reporter ?? _reporter,
         pubServePort: pubServePort ?? pubServeUrl?.port,
         concurrency: concurrency ?? _concurrency,