GN Build fixes for Flutter + gen_snapshot fix

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 'dart:io' show Directory, Platform;
 
 import 'runtime_configuration.dart' show RuntimeConfiguration;
 
 import 'test_runner.dart' show Command, CommandBuilder, CompilationCommand;
 
 import 'test_suite.dart' show TestInformation, TestUtils;
 
 /// Grouping of a command with its expected result.
 class CommandArtifact {
   final List<Command> commands;
@@ skipping 308 matching lines @@
           CommandBuilder.instance, arguments, environmentOverrides)
     ], '$tempDir', 'application/dart-precompiled');
   }
 
   CompilationCommand computeCompilationCommand(
       String tempDir,
       String buildDir,
       CommandBuilder commandBuilder,
       List arguments,
       Map<String, String> environmentOverrides) {
-    var exec = "$buildDir/dart_bootstrap";
+    var sourceDir = Directory.current.path;
+    var exec = "$buildDir/gen_snapshot";
     var args = new List();
-    args.add("--gen-precompiled-snapshot=$tempDir");
+
+    var precompiledVMIsolate = "$tempDir/precompiled.vmisolate";
+    var precompiledIsolate = "$tempDir/precompiled.isolate";
+    var precompiledInstructions = "$tempDir/precompiled.S";
+    var dartProductEntries = "$sourceDir/runtime/bin/dart_product_entries.txt";
+    var dartEntries = "$sourceDir/runtime/bin/dart_entries.txt";
+    var vmServiceIoMain = "$sourceDir/runtime/bin/vmservice/vmservice_io.dart";
+
+    args.add("--embedder_entry_points_manifest=$dartProductEntries");
+    args.add("--embedder_entry_points_manifest=$dartEntries");

[rmacnak, 2016/04/20 22:56:04]

if (!product) {
  args.add("--embedder_entry_points_manifest=$dartEntries");
}

[Cutch, 2016/04/21 15:00:56]

Done.

+    args.add("--vm_isolate_snapshot=$precompiledVMIsolate");
+    args.add("--isolate_snapshot=$precompiledIsolate");
+    args.add("--instructions_snapshot=$precompiledInstructions");
+    args.add("--url_mapping=dart:vmservice_io,$vmServiceIoMain");
     args.addAll(arguments);
 
     return commandBuilder.getCompilationCommand('precompiler', tempDir, !useSdk,
         bootstrapDependencies(buildDir), exec, args, environmentOverrides);
   }
 
   CompilationCommand computeAssembleCommand(
       String tempDir,
       String buildDir,
       CommandBuilder commandBuilder,
@@ skipping 240 matching lines @@
       RuntimeConfiguration runtimeConfiguration,
       String buildDir,
       TestInformation info,
       List<String> vmOptions,
       List<String> sharedOptions,
       List<String> originalArguments,
       CommandArtifact artifact) {
     return <String>[];
   }
 }