Fuchsia: Adds File::Copy()

runtime/tests/vm/dart/hello_fuchsia_test.dart

 // Copyright (c) 2016, 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.
 
 import "dart:async";
 import "dart:convert";
 import "dart:io";
 
 testAddressParse() async {
   print(new InternetAddress("1.0.2.3").rawAddress);
@@ skipping 385 matching lines @@
 }
 
 void testPlatformEnvironment() {
   Map<String, String> env = Platform.environment;
   for (String k in env.keys) {
     String v = env[k];
     print("$k = '$v'");
   }
 }
 
+Future testCopy() async {
+  final String sourceName = "foo";
+  final String destName = "bar";
+  Directory tmp = await Directory.systemTemp.createTemp("testCopy");
+  File sourceFile = new File("${tmp.path}/$sourceName");
+  File destFile = new File("${tmp.path}/$destName");
+  List<int> data = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

[siva, 2016/12/20 00:04:22]

I think we should make this data bigger (potentially > 8k) to ensure we trigger
at least two iterations in the copy loop.

[zra, 2016/12/20 17:43:58]

Changed to 10KB.

+  await sourceFile.writeAsBytes(data);
+  await sourceFile.copy(destFile.path);
+  List<int> resultData = await destFile.readAsBytes();
+  assert(data.length == resultData.length);
+  for (int i = 0; i < data.length; i++) {
+    assert(data[i] == resultData[i]);
+  }
+  await sourceFile.delete();
+  await destFile.delete();
+  await tmp.delete();
+}
+
 main() async {
   print("Hello, Fuchsia!");
 
   print("testAddressParse");
   await testAddressParse();
   print("testAddressParse done");
 
   print("testSimpleBind");
   await testSimpleBind();
   print("testSimpleBind done");
@@ skipping 23 matching lines @@
   print("lsTest done");
 
   print("testPlatformEnvironment");
   testPlatformEnvironment();
   print("testPlatformEnvironment done");
 
   print("testProcess");
   await testProcess();
   print("testProcess done");
 
+  print("testCopy");
+  await testCopy();
+  print("testCopy done");
+
   print("Goodbyte, Fuchsia!");
 }