Include referrer chain with inline install requests.

chrome/browser/extensions/webstore_standalone_installer.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/browser/extensions/webstore_standalone_installer.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "base/values.h"
@@ skipping 51 matching lines @@
   }
 
   // Use the requesting page as the referrer both since that is more correct
   // (it is the page that caused this request to happen) and so that we can
   // track top sites that trigger inline install requests.
   webstore_data_fetcher_.reset(new WebstoreDataFetcher(
       this,
       profile_->GetRequestContext(),
       GetRequestorURL(),
       id_));
-  webstore_data_fetcher_->Start();
+  OnBeforeWebstoreDataRequest(webstore_data_fetcher_.get());

[Devlin, 2017/01/27 20:31:34]

(Following up from the other comment)

So here, we'd just do something like:
std::string json_data = GetJsonPostData();
if (!json_data.empty())
  webstore_data_fetcher_->SetJsonPostData(json_data);
webstore_data_fetcher_->Start();

[robertshield, 2017/01/28 03:58:48]

Done.

 }
 
 //
 // Private interface implementation.
 //
 
 WebstoreStandaloneInstaller::~WebstoreStandaloneInstaller() {
 }
 
 void WebstoreStandaloneInstaller::RunCallback(bool success,
@@ skipping 69 matching lines @@
             &error);
   }
   return localized_extension_for_display_.get();
 }
 
 void WebstoreStandaloneInstaller::InitInstallData(
     ActiveInstallData* install_data) const {
   // Default implementation sets no properties.
 }
 
+void WebstoreStandaloneInstaller::OnBeforeWebstoreDataRequest(
+    WebstoreDataFetcher* fetcher) {
+  webstore_data_fetcher_->Start();
+}
+
 void WebstoreStandaloneInstaller::OnManifestParsed() {
   ProceedWithInstallPrompt();
 }
 
 std::unique_ptr<ExtensionInstallPrompt>
 WebstoreStandaloneInstaller::CreateInstallUI() {
   return base::MakeUnique<ExtensionInstallPrompt>(GetWebContents());
 }
 
 std::unique_ptr<WebstoreInstaller::Approval>
@@ skipping 237 matching lines @@
 void WebstoreStandaloneInstaller::OnWebStoreDataFetcherDone() {
   // An instance of this class is passed in as a delegate for the
   // WebstoreInstallHelper, ExtensionInstallPrompt and WebstoreInstaller, and
   // therefore needs to remain alive until they are done. Clear the webstore
   // data fetcher to avoid calling Release in AbortInstall while any of these
   // operations are in progress.
   webstore_data_fetcher_.reset();
 }
 
 }  // namespace extensions