Save As for content retrieved via POST works in most circumstances.

content/browser/renderer_host/resource_dispatcher_host.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.
 
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
 
 #include "content/browser/renderer_host/resource_dispatcher_host.h"
 
 #include <set>
 #include <vector>
@@ skipping 875 matching lines @@
     const content::ResourceContext& context) {
   if (is_shutdown_)
     return net::ERR_INSUFFICIENT_RESOURCES;
 
   const GURL& url = request->original_url();
   const net::URLRequestContext* request_context = context.request_context();
   request->set_referrer(MaybeStripReferrer(GURL(request->referrer())).spec());
   request->set_context(request_context);
   int extra_load_flags = net::LOAD_IS_DOWNLOAD;
   if (prefer_cache) {
-    extra_load_flags |= net::LOAD_PREFERRING_CACHE;
+    // If there is upload data attached, only retrieve from cache because there
+    // is no current mechanism to prompt the user for their consent for a
+    // re-post. For GETs, try to retrieve data from the cache and skip
+    // validating the entry if present.
+    if (request->get_upload() != NULL)
+      extra_load_flags |= net::LOAD_ONLY_FROM_CACHE;
+    else
+      extra_load_flags |= net::LOAD_PREFERRING_CACHE;
   } else {
     extra_load_flags |= net::LOAD_DISABLE_CACHE;
   }
   request->set_load_flags(request->load_flags() | extra_load_flags);
   // Check if the renderer is permitted to request the requested URL.
   if (!ChildProcessSecurityPolicy::GetInstance()->
           CanRequestURL(child_id, url)) {
     VLOG(1) << "Denied unauthorized download request for "
             << url.possibly_invalid_spec();
     return net::ERR_ACCESS_DENIED;
@@ skipping 1361 matching lines @@
   scoped_refptr<ResourceHandler> transferred_resource_handler(
       new DoomedResourceHandler(info->resource_handler()));
   info->set_resource_handler(transferred_resource_handler.get());
 }
 
 bool ResourceDispatcherHost::IsTransferredNavigation(
     const content::GlobalRequestID& transferred_request_id) const {
   return transferred_navigations_.find(transferred_request_id) !=
       transferred_navigations_.end();
 }