Dart2js testing: Add prefix files when running dart2js output on d8 or jsshell.

tools/testing/dart/runtime_configuration.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library runtime_configuration;
 
 import 'compiler_configuration.dart' show
     CommandArtifact;
 
 // TODO(ahe): Remove this import, we can precompute all the values required
 // from TestSuite once the refactoring is complete.
 import 'test_suite.dart' show
     TestSuite;
 
 import 'test_runner.dart' show
     Command,
     CommandBuilder;
 
+import 'utils.dart' show
+    Path;
+
 // TODO(ahe): I expect this class will become abstract very soon.
 class RuntimeConfiguration {
   // TODO(ahe): Remove this constructor and move the switch to
   // test_options.dart.  We probably want to store an instance of
   // [RuntimeConfiguration] in [configuration] there.
   factory RuntimeConfiguration(Map configuration) {
     String runtime = configuration['runtime'];
     switch (runtime) {
       case 'ContentShellOnAndroid':
       case 'DartiumOnAndroid':
@@ skipping 40 matching lines @@
 
   List<Command> computeRuntimeCommands(
       TestSuite suite,
       CommandBuilder commandBuilder,
       CommandArtifact artifact,
       List<String> arguments,
       Map<String, String> environmentOverrides) {
     // TODO(ahe): Make this method abstract.
     throw "Unimplemented runtime '$runtimeType'";
   }
+
+  List<String> dart2jsPreambles(Path preambleDir) => [];
 }
 
 /// The 'none' runtime configuration.
 class NoneRuntimeConfiguration extends RuntimeConfiguration {
   NoneRuntimeConfiguration()
       : super._subclass();
 
   List<Command> computeRuntimeCommands(
       TestSuite suite,
       CommandBuilder commandBuilder,
@@ skipping 28 matching lines @@
       CommandBuilder commandBuilder,
       CommandArtifact artifact,
       List<String> arguments,
       Map<String, String> environmentOverrides) {
     // TODO(ahe): Avoid duplication of this method between d8 and jsshell.
     checkArtifact(artifact);
     return <Command>[
         commandBuilder.getJSCommandlineCommand(
             moniker, suite.d8FileName, arguments, environmentOverrides)];
   }
+
+  List<String> dart2jsPreambles(Path preambleDir) {
+    return [preambleDir.append('d8.js').toNativePath()];
+  }
 }
 
 /// Firefox/SpiderMonkey-based development shell (jsshell).
 class JsshellRuntimeConfiguration extends CommandLineJavaScriptRuntime {
   JsshellRuntimeConfiguration()
       : super('jsshell');
 
   List<Command> computeRuntimeCommands(
       TestSuite suite,
       CommandBuilder commandBuilder,
       CommandArtifact artifact,
       List<String> arguments,
       Map<String, String> environmentOverrides) {
     checkArtifact(artifact);
     return <Command>[
         commandBuilder.getJSCommandlineCommand(
             moniker, suite.jsShellFileName, arguments, environmentOverrides)];
   }
+
+  List<String> dart2jsPreambles(Path preambleDir) {
+    return ['-f', preambleDir.append('jsshell.js').toNativePath(), '-f'];
+  }
 }
 
 /// Common runtime configuration for runtimes based on the Dart VM.
 class DartVmRuntimeConfiguration extends RuntimeConfiguration {
   DartVmRuntimeConfiguration()
       : super._subclass();
 
   int computeTimeoutMultiplier({
       bool isDebug: false,
       bool isChecked: false,
@@ skipping 54 matching lines @@
 class DummyRuntimeConfiguration extends DartVmRuntimeConfiguration {
   List<Command> computeRuntimeCommands(
       TestSuite suite,
       CommandBuilder commandBuilder,
       CommandArtifact artifact,
       List<String> arguments,
       Map<String, String> environmentOverrides) {
     throw "Unimplemented runtime '$runtimeType'";
   }
 }