Add retry writing to DevFS. (#8142)

This is a workaround to #8141

packages/flutter_tools/lib/src/devfs.dart

@@ -222,6 +222,7 @@ class _DevFSHttpWriter {
   final Uri httpAddress;
 
   static const int kMaxInFlight = 6;
+  static const int kMaxRetries = 3;
 
   int _inFlight = 0;
   Map<String, DevFSContent> _outstanding;
@@ -256,9 +257,12 @@ class _DevFSHttpWriter {
     }
   }
 
-  Future<Null> _scheduleWrite(String devicePath,
+  Future<Null> _scheduleWrite(
+    String devicePath,
     DevFSContent content,
-                              DevFSProgressReporter progressReporter) async {
+    DevFSProgressReporter progressReporter, [
+    int retry = 0,
+  ]) async {
     try {
       HttpClientRequest request = await _client.putUrl(httpAddress);
       request.headers.removeAll(HttpHeaders.ACCEPT_ENCODING);
@@ -270,8 +274,14 @@ class _DevFSHttpWriter {
       HttpClientResponse response = await request.close();
       await response.drain<Null>();
     } catch (e) {
+      if (retry < kMaxRetries) {
+        printTrace('Retrying writing "$devicePath" to DevFS due to error: $e');
+        _scheduleWrite(devicePath, content, progressReporter, retry + 1);
+        return;
+      } else {
         printError('Error writing "$devicePath" to DevFS: $e');
       }
+    }
     if (progressReporter != null) {
       _done++;
       progressReporter(_done, _max);