Fix a crashing call to GURL::spec() in downloads_api.cc:DownloadItemToJSON()

content/browser/download/download_manager_impl.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_manager_impl.h"
 
 #include <iterator>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 39 matching lines @@
 
 void BeginDownload(scoped_ptr<DownloadUrlParameters> params,
                    DownloadId download_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   // ResourceDispatcherHost{Base} is-not-a URLRequest::Delegate, and
   // DownloadUrlParameters can-not include resource_dispatcher_host_impl.h, so
   // we must down cast. RDHI is the only subclass of RDH as of 2012 May 4.
   scoped_ptr<net::URLRequest> request(
       params->resource_context()->GetRequestContext()->CreateRequest(
           params->url(), NULL));
-  request->set_referrer(params->referrer().url.spec());
+  if (params->referrer().url.is_valid())
+    request->set_referrer(params->referrer().url.spec());
   webkit_glue::ConfigureURLRequestForReferrerPolicy(
       request.get(), params->referrer().policy);
   request->set_load_flags(request->load_flags() | params->load_flags());
   request->set_method(params->method());
   if (!params->post_body().empty()) {
     const std::string& body = params->post_body();
     scoped_ptr<net::UploadElementReader> reader(
         net::UploadOwnedBytesElementReader::CreateWithString(body));
     request->set_upload(make_scoped_ptr(
         net::UploadDataStream::CreateWithReader(reader.Pass(), 0)));
@@ skipping 597 matching lines @@
   if (delegate_)
     delegate_->OpenDownload(download);
 }
 
 void DownloadManagerImpl::ShowDownloadInShell(DownloadItemImpl* download) {
   if (delegate_)
     delegate_->ShowDownloadInShell(download);
 }
 
 }  // namespace content