Fuchsia: Adds File::Copy()

runtime/tests/vm/dart/hello_fuchsia_test.dart

Index: runtime/tests/vm/dart/hello_fuchsia_test.dart
diff --git a/runtime/tests/vm/dart/hello_fuchsia_test.dart b/runtime/tests/vm/dart/hello_fuchsia_test.dart
index ce9cd7da7fe07ea3b22ca17885b71472a80364d1..1acd69796306cd658fcae5adb8b5d0ab3b7258c8 100644
--- a/runtime/tests/vm/dart/hello_fuchsia_test.dart
+++ b/runtime/tests/vm/dart/hello_fuchsia_test.dart
@@ -403,6 +403,25 @@ void testPlatformEnvironment() {
   }
 }
 
+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!");
 
@@ -446,5 +465,9 @@ main() async {
   await testProcess();
   print("testProcess done");
 
+  print("testCopy");
+  await testCopy();
+  print("testCopy done");
+
   print("Goodbyte, Fuchsia!");
 }