NOT YET READY: Making chrome.windows.create establish an actual "opener" relationship.

chrome/browser/ui/browser_navigator.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/ui/browser_navigator.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/macros.h"
@@ skipping 16 matching lines @@
 #include "chrome/browser/ui/search/instant_search_prerenderer.h"
 #include "chrome/browser/ui/singleton_tabs.h"
 #include "chrome/browser/ui/status_bubble.h"
 #include "chrome/browser/ui/tab_helpers.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/url_constants.h"
 #include "components/prefs/pref_service.h"
 #include "content/public/browser/browser_url_handler.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/notification_service.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
 #include "extensions/features/features.h"
 
 #if defined(USE_ASH)
 #include "chrome/browser/ui/ash/multi_user/multi_user_window_manager.h"
 #include "components/signin/core/account_id/account_id.h"
 #endif
 
 #if defined(USE_AURA)
@@ skipping 304 matching lines @@
  private:
   chrome::NavigateParams* params_;
   std::unique_ptr<WebContents> target_contents_owner_;
   DISALLOW_COPY_AND_ASSIGN(ScopedTargetContentsOwner);
 };
 
 content::WebContents* CreateTargetContents(const chrome::NavigateParams& params,
                                            const GURL& url) {
   WebContents::CreateParams create_params(
       params.browser->profile(),
-      params.source_site_instance && !params.force_new_process_for_new_contents
-          ? params.source_site_instance

[Charlie Reis, 2017/06/05 21:06:28]

Was this really only used for chrome.windows.create?  Huh.  I suppose having
this process decision line up with whether an opener is defined is ok, though it
might help to have a comment to that effect.

One sanity check: It appears we're changing the default behavior, but I'm not
sure if that results in an observable change.  Before,
force_new_process_for_new_contents defaulted to false, and thus we would use
params.source_site_instance for any case that didn't explicitly set it to true. 
Now, opener defaults to null, so we use GetSiteInstanceForNewTab for any case
that doesn't explicitly define it.

The cases I know about are chrome.windows.create (which set it to false before
and now sets the opener, preserving behavior) and RenderFrameHostImpl::OnOpenURL
(which set it to true before and doesn't set the opener, preserving behavior).

There are over 100 calls to Navigate, so it's possible others could be affected.
 It looks like the only one that assigns source_site_instance is
chrome.windows.create, though, so I *think* all the rest hit the
GetSiteInstanceForNewTab call before and will after as well.  Does that sound
right?

[Łukasz Anforowicz, 2017/06/05 22:06:54]

I've added a comment here.
Right - the main thing here is that chrome::NavigateParams::source_site_instance
was/is only set by 1) chrome.windows.create API and 2)
NavigatorImpl::RequestOpenURL (via content::OpenURLParams).  The new behavior
should be matching expectations in these two cases.

+      params.opener
+          ? params.opener->GetSiteInstance()
           : tab_util::GetSiteInstanceForNewTab(params.browser->profile(), url));
   create_params.main_frame_name = params.frame_name;
+  if (params.opener) {
+    create_params.opener_render_frame_id = params.opener->GetRoutingID();
+    create_params.opener_render_process_id =
+        params.opener->GetProcess()->GetID();
+  }
   if (params.source_contents) {
     create_params.initial_size =
         params.source_contents->GetContainerBounds().size();
     create_params.created_with_opener = params.created_with_opener;
   }
   if (params.disposition == WindowOpenDisposition::NEW_BACKGROUND_TAB)
     create_params.initially_hidden = true;
 
 #if defined(USE_AURA)
   if (params.browser->window() &&
@@ skipping 91 matching lines @@
       }
     }
   }
 #endif
 
   // Navigate() must not return early after this point.
 
   if (GetSourceProfile(params) != params->browser->profile()) {
     // A tab is being opened from a link from a different profile, we must reset
     // source information that may cause state to be shared.
+    params->opener = nullptr;
     params->source_contents = nullptr;
     params->source_site_instance = nullptr;
     params->referrer = content::Referrer();
   }
 
   // Make sure the Browser is shown if params call for it.
   ScopedBrowserShower shower(params);
 
   // Makes sure any WebContents created by this function is destroyed if
   // not properly added to a tab strip.
@@ skipping 190 matching lines @@
   bool reverse_on_redirect = false;
   content::BrowserURLHandler::GetInstance()->RewriteURLIfNecessary(
       &rewritten_url, browser_context, &reverse_on_redirect);
 
   // Some URLs are mapped to uber subpages. Do not allow them in incognito.
   return !(rewritten_url.scheme_piece() == content::kChromeUIScheme &&
            rewritten_url.host_piece() == chrome::kChromeUIUberHost);
 }
 
 }  // namespace chrome