Add support to dart2js for option --enable-asserts.

tools/testing/dart/compiler_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 compiler_configuration;
 
 import 'dart:io' show Platform;
 
 import 'runtime_configuration.dart' show RuntimeConfiguration;
 import 'runtime_configuration.dart' show DartPrecompiledAdbRuntimeConfiguration;
@@ skipping 49 matching lines @@
     bool isChecked = configuration['checked'];
     bool isStrong = configuration['strong'];
     bool isHostChecked = configuration['host_checked'];
     bool useSdk = configuration['use_sdk'];
     bool isCsp = configuration['csp'];
     bool useCps = configuration['cps_ir'];
     bool useBlobs = configuration['use_blobs'];
     bool hotReload = configuration['hot_reload'];
     bool hotReloadRollback = configuration['hot_reload_rollback'];
     bool useFastStartup = configuration['fast_startup'];
+    bool useEnableAsserts = configuration['enable_asserts'];
     bool useKernelInDart2js = configuration['dart2js_with_kernel'];
 
     switch (compiler) {
       case 'dart2analyzer':
         return new AnalyzerCompilerConfiguration(
             isDebug: isDebug,
             isChecked: isChecked,
             isStrong: isStrong,
             isHostChecked: isHostChecked,
             useSdk: useSdk);
       case 'dart2js':
         return new Dart2jsCompilerConfiguration(
             isDebug: isDebug,
             isChecked: isChecked,
             isHostChecked: isHostChecked,
             useCps: useCps,
             useSdk: useSdk,
             isCsp: isCsp,
             useFastStartup: useFastStartup,
+            useEnableAsserts: useEnableAsserts,
             useKernel: useKernelInDart2js,
             extraDart2jsOptions:
                 TestUtils.getExtraOptions(configuration, 'dart2js_options'));
       case 'app_jit':
         return new AppJitCompilerConfiguration(
             isDebug: isDebug, isChecked: isChecked);
       case 'precompiler':
         return new PrecompilerCompilerConfiguration(
             isDebug: isDebug,
             isChecked: isChecked,
@@ skipping 433 matching lines @@
                   .resolve('dart-sdk/bin/snapshots/dart2js.dart.snapshot')
             ]);
   }
 }
 
 /// Configuration for dart2js compiler.
 class Dart2jsCompilerConfiguration extends Dart2xCompilerConfiguration {
   final bool isCsp;
   final bool useCps;
   final bool useFastStartup;
+  final bool useEnableAsserts;
   final bool useKernel;
   final List<String> extraDart2jsOptions;
   // We cache the extended environment to save memory.
   static Map<String, String> cpsFlagCache;
   static Map<String, String> environmentOverridesCacheObject;
 
   Dart2jsCompilerConfiguration(
       {bool isDebug,
       bool isChecked,
       bool isHostChecked,
       bool useSdk,
       bool this.useCps,
       bool this.isCsp,
       bool this.useFastStartup,
+      bool this.useEnableAsserts,
       this.useKernel,
       this.extraDart2jsOptions})
       : super('dart2js',
             isDebug: isDebug,
             isChecked: isChecked,
             isHostChecked: isHostChecked,
             useSdk: useSdk);
 
   int computeTimeoutMultiplier() {
     int multiplier = 1;
@@ skipping 391 matching lines @@
       RuntimeConfiguration runtimeConfiguration,
       String buildDir,
       TestInformation info,
       List<String> vmOptions,
       List<String> sharedOptions,
       List<String> originalArguments,
       CommandArtifact artifact) {
     return <String>[];
   }
 }