Add an HTTP client based on Curl.

pkg/http/lib/src/utils.dart

Index: pkg/http/lib/src/utils.dart
diff --git a/pkg/http/lib/src/utils.dart b/pkg/http/lib/src/utils.dart
index 02a0f7e0fbce1dfdf3befc43ad606f4a35c21a0e..9f22351643331e52cb32cbb8145cecc820d8fa47 100644
--- a/pkg/http/lib/src/utils.dart
+++ b/pkg/http/lib/src/utils.dart
@@ -183,3 +183,26 @@ Future forEachFuture(Iterable input, Future fn(element)) {
   }
   return nextElement(null);
 }
+
+/// Creates a temporary directory and passes its path to [fn]. Once the [Future]
+/// returned by [fn] completes, the temporary directory and all its contents
+/// will be deleted.
+Future withTempDir(Future fn(String path)) {
+  var tempDir;
+  var future = new Directory('').createTemp().chain((dir) {
+    tempDir = dir;
+    return fn(tempDir.path);
+  });
+  future.onComplete((_) => tempDir.delete(recursive: true));
+  return future;
+}
+
+/// Configures [future] so that its result (success or exception) is passed on
+/// to [completer].
+void chainToCompleter(Future future, Completer completer) {
+  future.handleException((e) {
+    completer.completeException(e);
+    return true;
+  });
+  future.then(completer.complete);
+}