Support paths which are encoded with base64 in http put devfs server code

runtime/observatory/tests/service/dev_fs_http_put_weird_char_test.dart

Index: runtime/observatory/tests/service/dev_fs_http_put_weird_char_test.dart
diff --git a/runtime/observatory/tests/service/dev_fs_http_put_test.dart b/runtime/observatory/tests/service/dev_fs_http_put_weird_char_test.dart
similarity index 92%
copy from runtime/observatory/tests/service/dev_fs_http_put_test.dart
copy to runtime/observatory/tests/service/dev_fs_http_put_weird_char_test.dart
index c5639a808c1cab590b2fd321ebe82bb932526ce3..517a83261eea841c0f95e7b74261dbdc8b7ddbb1 100644
--- a/runtime/observatory/tests/service/dev_fs_http_put_test.dart
+++ b/runtime/observatory/tests/service/dev_fs_http_put_weird_char_test.dart
@@ -21,10 +21,11 @@ Future<String> readResponse(HttpClientResponse response) {
 
 
 var tests = [
-  // Write a file with the ? character in the filename.
+  // Write a file with the \r character in the filename.
   (VM vm) async {
     var fsId = 'test';
-    var filePath = '/foo/bar.dat';
+    var filePath = '/foo/b\rar.dart';
+    var filePathBase64 = BASE64.encode(UTF8.encode(filePath));
     var fileContents = [0, 1, 2, 3, 4, 5, 6, 255];
     var fileContentsBase64 = BASE64.encode(fileContents);
 
@@ -40,7 +41,7 @@ var tests = [
     HttpClientRequest request =
         await client.putUrl(Uri.parse(serviceHttpAddress));
     request.headers.add('dev_fs_name', fsId);
-    request.headers.add('dev_fs_path', filePath);
+    request.headers.add('dev_fs_path_b64', filePathBase64);
     request.add(GZIP.encode([9]));
     HttpClientResponse response = await request.close();
     String responseBody = await readResponse(response);
@@ -64,7 +65,7 @@ var tests = [
     request =
         await client.putUrl(Uri.parse(serviceHttpAddress));
     request.headers.add('dev_fs_name', fsId);
-    request.headers.add('dev_fs_path', filePath);
+    request.headers.add('dev_fs_path_b64', filePathBase64);
     request.add(GZIP.encode(fileContents));
     response = await request.close();
     responseBody = await readResponse(response);