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

chrome/browser/extensions/api/tabs/tabs_api.cc

Index: chrome/browser/extensions/api/tabs/tabs_api.cc
diff --git a/chrome/browser/extensions/api/tabs/tabs_api.cc b/chrome/browser/extensions/api/tabs/tabs_api.cc
index a3b16919c5a6d9bc840574dac92ec7706a7622ca..4cd7223e3b7585ef3b4141ef74aedc90c10c0d67 100644
--- a/chrome/browser/extensions/api/tabs/tabs_api.cc
+++ b/chrome/browser/extensions/api/tabs/tabs_api.cc
@@ -570,14 +570,7 @@ ExtensionFunction::ResponseAction WindowsCreateFunction::Run() {
     chrome::NavigateParams navigate_params(new_window, url,
                                            ui::PAGE_TRANSITION_LINK);
     navigate_params.disposition = WindowOpenDisposition::NEW_FOREGROUND_TAB;
-
-    // The next 2 statements put the new contents in the same BrowsingInstance
-    // as their opener.  Note that |force_new_process_for_new_contents = false|
-    // means that new contents might still end up in a new renderer
-    // (if they open a web URL and are transferred out of an extension
-    // renderer), but even in this case the flags below ensure findability via
-    // window.open.
-    navigate_params.force_new_process_for_new_contents = false;
+    navigate_params.opener = render_frame_host();

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

Worth keeping a comment saying that the intention is to stay in the same
BrowsingInstance.

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

Done.

     navigate_params.source_site_instance =
         render_frame_host()->GetSiteInstance();