[Downloads] Don't store or use validators unless they are strong.

ETag and Last-Modified headers shouldn't be used unless they imply
byte-wise equivalence. While RFC 2616 states that a client 'MAY' use them
anyway, we are going to be conservative and only use them if they are
strong.

BUG=7648

Review URL: https://codereview.chromium.org/67883007

git-svn-id: http://src.chromium.org/svn/trunk/src/net/tools/testserver@237349 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
diff --git a/testserver.py b/testserver.py
index e0317e8..f028497 100755
--- a/testserver.py
+++ b/testserver.py
@@ -1478,6 +1478,8 @@
     if not self._ShouldHandleRequest('/rangereset'):
       return False
 
+    # HTTP/1.1 is required for ETag and range support.
+    self.protocol_version = 'HTTP/1.1'
     _, _, url_path, _, query, _ = urlparse.urlparse(self.path)
 
     # Defaults