Make sure the --site-per-process flag is present for subframe process swaps.

content/browser/loader/cross_site_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/loader/cross_site_resource_handler.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 50 matching lines @@
 };
 
 void OnCrossSiteResponseHelper(const CrossSiteResponseParams& params) {
   scoped_ptr<CrossSiteTransferringRequest> cross_site_transferring_request(
       new CrossSiteTransferringRequest(params.global_request_id));
 
   RenderFrameHostImpl* rfh =
       RenderFrameHostImpl::FromID(params.global_request_id.child_id,
                                   params.render_frame_id);
   if (rfh) {
+    if (rfh->GetParent()) {
+      // We should only swap processes for subframes in --site-per-process mode.
+      // CrossSiteResourceHandler is not installed on subframe requests in
+      // default Chrome.
+      CHECK(base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kSitePerProcess));
+    }
     rfh->OnCrossSiteResponse(
         params.global_request_id, cross_site_transferring_request.Pass(),
         params.transfer_url_chain, params.referrer,
         params.page_transition, params.should_replace_current_entry);
   } else if (leak_requests_for_testing_ && cross_site_transferring_request) {
     // Some unit tests expect requests to be leaked in this case, so they can
     // pass them along manually.
     cross_site_transferring_request->ReleaseRequest();
   }
 }
@@ skipping 341 matching lines @@
     controller()->Resume();
   }
 }
 
 void CrossSiteResourceHandler::OnDidDefer() {
   did_defer_ = true;
   request()->LogBlockedBy("CrossSiteResourceHandler");
 }
 
 }  // namespace content