PlzNavigate: set the right cache policy on back POST navigations

content/browser/frame_host/navigation_request.cc

 // Copyright 2014 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/frame_host/navigation_request.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "content/browser/appcache/appcache_navigation_handle.h"
@@ skipping 57 matching lines @@
       break;
     case FrameMsg_Navigate_Type::RESTORE:
       *load_flags |= net::LOAD_SKIP_CACHE_VALIDATION;
       break;
     case FrameMsg_Navigate_Type::RESTORE_WITH_POST:
       *load_flags |=
           net::LOAD_ONLY_FROM_CACHE | net::LOAD_SKIP_CACHE_VALIDATION;
       break;
     case FrameMsg_Navigate_Type::SAME_DOCUMENT:
     case FrameMsg_Navigate_Type::DIFFERENT_DOCUMENT:
+      if (is_post)
+        *load_flags |= net::LOAD_VALIDATE_CACHE;
+      break;
     case FrameMsg_Navigate_Type::HISTORY_SAME_DOCUMENT:
     case FrameMsg_Navigate_Type::HISTORY_DIFFERENT_DOCUMENT:
-      if (is_post)
-        *load_flags |= net::LOAD_VALIDATE_CACHE;
+      if (is_post) {
+        *load_flags |=
+            net::LOAD_ONLY_FROM_CACHE | net::LOAD_SKIP_CACHE_VALIDATION;
+      }
       break;
   }
 }
 
 // TODO(clamy): This should be function in FrameTreeNode.
 bool IsSecureFrame(FrameTreeNode* frame) {
   while (frame) {
     if (!IsPotentiallyTrustworthyOrigin(frame->current_origin()))
       return false;
     frame = frame->parent();
@@ skipping 635 matching lines @@
   DCHECK_EQ(request_params_.has_user_gesture, begin_params_.has_user_gesture);
 
   render_frame_host->CommitNavigation(response_.get(), std::move(body_),
                                       common_params_, request_params_,
                                       is_view_source_);
 
   frame_tree_node_->ResetNavigationRequest(true);
 }
 
 }  // namespace content