Add option to HttpClient to turn of auto uncompression

sdk/lib/io/http_impl.dart

Index: sdk/lib/io/http_impl.dart
diff --git a/sdk/lib/io/http_impl.dart b/sdk/lib/io/http_impl.dart
index b0a1d8fb35b4847b094593bf2f02beb3a96482f4..7b80d6a7c14802161fa92ea5e68f7f3087e33fe2 100644
--- a/sdk/lib/io/http_impl.dart
+++ b/sdk/lib/io/http_impl.dart
@@ -270,7 +270,8 @@ class _HttpClientResponse
       return new Stream.fromIterable([]).listen(null, onDone: onDone);
     }
     var stream = _incoming;
-    if (headers.value(HttpHeaders.CONTENT_ENCODING) == "gzip") {
+    if (_httpClient.autoUncompress &&
+        headers.value(HttpHeaders.CONTENT_ENCODING) == "gzip") {
       stream = stream.transform(GZIP.decoder);
     }
     return stream.listen(onData,
@@ -1650,6 +1651,8 @@ class _HttpClient implements HttpClient {
 
   int maxConnectionsPerHost;
 
+  bool autoUncompress = true;
+
   String userAgent = _getHttpVersion();
 
   void set idleTimeout(Duration timeout) {