Emit CSP code in separate file.

dart/tests/compiler/dart2js/memory_compiler.dart

 // Copyright (c) 2013, 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 dart2js.test.memory_compiler;
 
 import 'package:expect/expect.dart';
 import 'memory_source_file_helper.dart';
 
 import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart'
@@ skipping 70 matching lines @@
                       bool showDiagnostics: true}) {
   Uri script = currentDirectory.resolve(nativeToUriPath(Platform.script));
   Uri libraryRoot = script.resolve('../../../sdk/');
   Uri packageRoot = script.resolve('./packages/');
 
   var provider = new MemorySourceFileProvider(memorySourceFiles);
   var handler =
       createDiagnosticHandler(diagnosticHandler, provider, showDiagnostics);
 
   EventSink<String> outputProvider(String name, String extension) {
-    if (name != '') throw 'Attempt to output file "$name.$extension"';
+    if (name != '' && name != 'precompiled') {
+      throw 'Attempt to output file "$name.$extension"';
+    }
     return new NullSink('$name.$extension');
   }
 
   Compiler compiler = new Compiler(provider.readStringFromUri,
                                    outputProvider,
                                    handler,
                                    libraryRoot,
                                    packageRoot,
                                    options);
   if (cachedCompiler != null) {
@@ skipping 43 matching lines @@
       createDiagnosticHandler(diagnosticHandler, provider, showDiagnostics);
 
   List<Uri> libraries = <Uri>[];
   memorySourceFiles.forEach((String path, _) {
     libraries.add(new Uri(scheme: 'memory', path: path));
   });
 
   return analyze(libraries, libraryRoot, packageRoot,
                  provider, handler, options);
 }