Use a single file for app snapshots.

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;
 
@@ skipping 351 matching lines @@
   }
 
   CompilationCommand computeCompilationCommand(
       String tempDir,
       String buildDir,
       CommandBuilder commandBuilder,
       List arguments,
       Map<String, String> environmentOverrides) {
     var exec = "$buildDir/dart_bootstrap";
     var args = new List();
-    args.add("--snapshot=$tempDir");
     args.add("--snapshot-kind=app-aot");
     if (useBlobs) {
+      args.add("--snapshot=$tempDir/out.aotsnapshot");
       args.add("--use-blobs");
+    } else {
+      args.add("--snapshot=$tempDir/out.S");
     }
     if (isAndroid && arch == 'arm') {
       args.add('--no-sim-use-hardfp');
     }
     args.addAll(arguments);
 
     return commandBuilder.getCompilationCommand('precompiler', tempDir, !useSdk,
         bootstrapDependencies(buildDir), exec, args, environmentOverrides);
   }
 
@@ skipping 38 matching lines @@
       cc_flags = "-EL";
     } else {
       throw "Architecture not supported: $arch";
     }
 
     var exec = cc;
     var args = (cc_flags != null) ? [ shared, cc_flags ] : [ shared ];
     args.addAll([
       '-o',
       '$tempDir/$libname',
-      '$tempDir/snapshot.S'
+      '$tempDir/out.S'
     ]);
 
     return commandBuilder.getCompilationCommand('assemble', tempDir, !useSdk,
         bootstrapDependencies(buildDir), exec, args, environmentOverrides);
   }
 
   // This step reduces the amount of space needed to run the precompilation
   // tests by 60%.
   CompilationCommand computeRemoveAssemblyCommand(
       String tempDir,
       String buildDir,
       CommandBuilder commandBuilder,
       List arguments,
       Map<String, String> environmentOverrides) {
     var exec = 'rm';
-    var args = ['$tempDir/snapshot.S'];
+    var args = ['$tempDir/out.S'];
 
     return commandBuilder.getCompilationCommand(
         'remove_assembly',
         tempDir,
         !useSdk,
         bootstrapDependencies(buildDir),
         exec,
         args,
         environmentOverrides);
   }
@@ skipping 64 matching lines @@
   }
 
   CompilationCommand computeCompilationCommand(
       String tempDir,
       String buildDir,
       CommandBuilder commandBuilder,
       List arguments,
       Map<String, String> environmentOverrides) {
     var exec = "$buildDir/dart_bootstrap";
     var args = new List();
-    args.add("--snapshot=$tempDir");
+    args.add("--snapshot=$tempDir/out.jitsnapshot");
     args.add("--snapshot-kind=app-after-run");
     args.addAll(arguments);
 
     return commandBuilder.getCompilationCommand(
         'dart2snapshot',
         tempDir,
         !useSdk,
         bootstrapDependencies(buildDir),
         exec,
         args,
@@ skipping 39 matching lines @@
       : super(isDebug: isDebug, isChecked: isChecked), this.useBlobs = useBlobs;
 
   CompilationCommand computeCompilationCommand(
       String tempDir,
       String buildDir,
       CommandBuilder commandBuilder,
       List arguments,
       Map<String, String> environmentOverrides) {
     var exec = "$buildDir/dart";
     var args = new List();
-    args.add("--snapshot=$tempDir");
+    args.add("--snapshot=$tempDir/out.jitsnapshot");
     args.add("--snapshot-kind=app-jit-after-run");
     if (useBlobs) {
       args.add("--use-blobs");
     }
     args.addAll(arguments);
 
     return commandBuilder.getCompilationCommand(
         'dart2snapshot',
         tempDir,
         !useSdk,
@@ skipping 62 matching lines @@
       RuntimeConfiguration runtimeConfiguration,
       String buildDir,
       TestInformation info,
       List<String> vmOptions,
       List<String> sharedOptions,
       List<String> originalArguments,
       CommandArtifact artifact) {
     return <String>[];
   }
 }