Allow top-level navigation in extension pop-ups if it only triggers a download.

chrome/renderer/chrome_content_renderer_client.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 "chrome/renderer/chrome_content_renderer_client.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/command_line.h"
@@ skipping 1078 matching lines @@
   // process if it is an Instant url, or to another process if not.  Conversely,
   // fork if this is a non-Instant process navigating to an Instant url, so that
   // such navigations can also be bucketed into an Instant renderer.
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kInstantProcess) ||
       SearchBouncer::GetInstance()->ShouldFork(url)) {
     *send_referrer = true;
     return true;
   }
 
+  // TODO(lukasza): https://crbug.com/650694: For now, we skip the rest for POST
+  // submissions.  This is because 1) in M54 there are some remaining issues
+  // with POST in OpenURL path (e.g. https://crbug.com/648648) and 2) OpenURL
+  // path regresses (blocks) navigations that result in downloads
+  // (https://crbug.com/646261).  In the long-term we should avoid forking for
+  // extensions (not hosted apps though) altogether and rely on transfers logic
+  // instead.
+  if (http_method != "GET")
+    return false;
+
   // If |url| matches one of the prerendered URLs, stop this navigation and try
   // to swap in the prerendered page on the browser process. If the prerendered
   // page no longer exists by the time the OpenURL IPC is handled, a normal
   // navigation is attempted.
   if (prerender_dispatcher_.get() &&
       prerender_dispatcher_->IsPrerenderURL(url)) {
     *send_referrer = true;
     return true;
   }
 
@@ skipping 370 matching lines @@
 
   url::Replacements<char> r;
   r.SetPath(path.c_str(), url::Component(0, path.length()));
 
   if (result == internal::NUM_PLUGIN_ERROR)
     result = invalid_url ? internal::SUCCESS_PARAMS_REWRITE : internal::SUCCESS;
 
   RecordYouTubeRewriteUMA(result);
   return corrected_url.ReplaceComponents(r);
 }