Revert the debugging changes that added vm abort flag and core dumps.

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
@@ skipping 199 matching lines @@
 
   CompilationCommand computeCompilationCommand(
       String outputFileName,
       String buildDir,
       CommandBuilder commandBuilder,
       List arguments,
       Map<String, String> environmentOverrides) {
     arguments = new List.from(arguments);
     arguments.add('--out=$outputFileName');
 
-    // We want all dart2js compilers to run the vm with the
-    // --abort-on-assertion-errors flag.
-    // We have allowed constant maps as environmentOverrides,
-    // so we modify a new map.
-    var newOverrides = {'DART_VM_OPTIONS': '--abort-on-assertion-errors'};
-    if (environmentOverrides != null) {
-      newOverrides.addAll(environmentOverrides);
-      if (environmentOverrides.containsKey('DART_VM_OPTIONS')) {
-        newOverrides['DART_VM_OPTIONS'] += ' --abort-on-assertion-errors';
-      }
-    }
     return commandBuilder.getCompilationCommand(
         moniker, outputFileName, !useSdk,
         bootstrapDependencies(buildDir),
         computeCompilerPath(buildDir),
-        arguments, newOverrides);
+        arguments, environmentOverrides);
   }
 
   List<Uri> bootstrapDependencies(String buildDir) {
     if (!useSdk) return const <Uri>[];
     return _bootstrapDependenciesCache.putIfAbsent(buildDir, () =>
       [Uri.base.resolveUri(nativeDirectoryToUri(buildDir))
                .resolve('dart-sdk/bin/snapshots/dart2js.dart.snapshot')]);
   }
 }
 
@@ skipping 294 matching lines @@
       RuntimeConfiguration runtimeConfiguration,
       String buildDir,
       TestInformation info,
       List<String> vmOptions,
       List<String> sharedOptions,
       List<String> originalArguments,
       CommandArtifact artifact) {
     return <String>[];
   }
 }