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

content/browser/download/download_resource_handler.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/download/download_resource_handler.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 150 matching lines @@
   RecordDownloadContentDisposition(info->content_disposition);
 
   info->request_handle =
       DownloadRequestHandle(AsWeakPtr(), request_info->GetChildID(),
                             request_info->GetRouteID(),
                             request_info->GetRequestID());
 
   // Get the last modified time and etag.
   const net::HttpResponseHeaders* headers = request()->response_headers();
   if (headers) {
-    // TODO(asanka): Only store these if headers->HasStrongValidators() is true.
-    //     See RFC 2616 section 13.3.3.
-    if (!headers->EnumerateHeader(NULL, "Last-Modified", &info->last_modified))
-      info->last_modified.clear();
-    if (!headers->EnumerateHeader(NULL, "ETag", &info->etag))
-      info->etag.clear();
+    if (headers->HasStrongValidators()) {
+      // If we don't have strong validators as per RFC 2616 section 13.3.3, then
+      // we neither store nor use them for range requests.
+      if (!headers->EnumerateHeader(NULL, "Last-Modified",
+                                    &info->last_modified))
+        info->last_modified.clear();
+      if (!headers->EnumerateHeader(NULL, "ETag", &info->etag))
+        info->etag.clear();
+    }
 
     int status = headers->response_code();
     if (2 == status / 100  && status != net::HTTP_PARTIAL_CONTENT) {
       // Success & not range response; if we asked for a range, we didn't
       // get it--reset the file pointers to reflect that.
       info->save_info->offset = 0;
       info->save_info->hash_state = "";
     }
 
     if (!headers->GetMimeType(&info->original_mime_type))
@@ skipping 277 matching lines @@
 
   // Remove output stream callback if a stream exists.
   if (stream_writer_)
     stream_writer_->RegisterCallback(base::Closure());
 
   UMA_HISTOGRAM_TIMES("SB2.DownloadDuration",
                       base::TimeTicks::Now() - download_start_time_);
 }
 
 }  // namespace content