Reenable some sample tests and fix how they find their data files

samples/sample_extension/test/sample_extension_test_helper.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.
 //
 // Dart test program for testing native extensions.
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
 
 import "package:expect/expect.dart";
 import "package:path/path.dart";
 
-Future copyFileToDirectory(String file, String directory) {
+Future copyFileToDirectory(String file, String directory) async {
   String src = file;
   String dst = directory;
+  ProcessResult result;
   switch (Platform.operatingSystem) {
     case 'linux':
     case 'macos':
-      return Process.run('cp', [src, dst]);
+      result = await Process.run('cp', [src, dst]);
+      break;
     case 'windows':
-      return Process.run('cmd.exe', ['/C', 'copy $src $dst']);
+      result = await Process.run('cmd.exe', ['/C', 'copy $src $dst']);
+      break;
     default:
       Expect.fail('Unknown operating system ${Platform.operatingSystem}');
   }
-}
-
-String getNativeLibraryPath(String buildDirectory) {
-  switch (Platform.operatingSystem) {
-    case 'linux':
-      return join(buildDirectory, 'lib.target', 'libsample_extension.so');
-    case 'macos':
-      return join(buildDirectory, 'libsample_extension.dylib');
-    case 'windows':
-      return join(buildDirectory, 'sample_extension.dll');
-    default:
-      Expect.fail('Unknown operating system ${Platform.operatingSystem}');
+  if (result.exitCode != 0) {
+    print(result.stdout);
+    print(result.stderr);
+    throw "Failed to copy test file ($file) to temporary directory ($directory)";
   }
 }
 
 Future run(String program, List arguments) async {
   print("+ $program ${arguments.join(' ')}");
   ProcessResult result = await Process.run(program, arguments);
   if (result.exitCode != 0) {
     print('Failing process stdout: ${result.stdout}');
     print('Failing process stderr: ${result.stderr}');
     print('End failing process stderr');
     Expect.fail('Test failed with exit code ${result.exitCode}');
   }
 }
 
 Future testNativeExtensions(String snapshotKind) async {
   String buildDirectory = dirname(Platform.executable);
   Directory tempDirectory =
       Directory.systemTemp.createTempSync('sample_extension_');
   try {
     String testDirectory = tempDirectory.path;
     String sourceDirectory = Platform.script.resolve('..').toFilePath();
 
-    // Copy sample_extension shared library, sample_extension dart files and
-    // sample_extension tests to the temporary test directory.
-    await copyFileToDirectory(getNativeLibraryPath(buildDirectory),
-                              testDirectory);
+    // Copy sample_extension dart files and sample_extension tests to the
+    // temporary test directory.
     for (var file in ['sample_synchronous_extension.dart',
                       'sample_asynchronous_extension.dart',
                       'test_sample_synchronous_extension.dart',
                       'test_sample_asynchronous_extension.dart']) {
       await copyFileToDirectory(join(sourceDirectory, file), testDirectory);
     }
 
     for (var test in ['test_sample_synchronous_extension.dart',
                       'test_sample_asynchronous_extension.dart']) {
       String script = join(testDirectory, test);
       String snapshot;
       if (snapshotKind == null) {
         snapshot = script;
       } else {
         snapshot = join(testDirectory, "$test.snapshot");
         await run(Platform.executable,
                   ['--snapshot=$snapshot',
                    '--snapshot-kind=$snapshotKind',
                    script]);
       }
 
       await run(Platform.executable, [snapshot]);
     }
   } finally {
     await tempDirectory.deleteSync(recursive: true);
   }
 }