Propagate opener to BackgroundsContents.

chrome/browser/ui/browser.cc

Index: chrome/browser/ui/browser.cc
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index 87bda12a8864d1a21c8cc277d822862a03c026f2..3e86d52efd89543117584010981358097240f602 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -1675,6 +1675,7 @@ void Browser::ShowRepostFormWarningDialog(WebContents* source) {
 
 bool Browser::ShouldCreateWebContents(
     content::WebContents* web_contents,
+    content::RenderFrameHost* opener,
     content::SiteInstance* source_site_instance,
     int32_t route_id,
     int32_t main_frame_route_id,
@@ -1689,7 +1690,7 @@ bool Browser::ShouldCreateWebContents(
       content::mojom::WindowContainerType::BACKGROUND) {
     // If a BackgroundContents is created, suppress the normal WebContents.
     return !MaybeCreateBackgroundContents(
-        source_site_instance, opener_url, route_id, main_frame_route_id,
+        source_site_instance, opener, opener_url, route_id, main_frame_route_id,
         main_frame_widget_route_id, frame_name, target_url, partition_id,
         session_storage_namespace);
   }
@@ -2551,6 +2552,7 @@ bool Browser::ShouldStartShutdown() const {
 
 bool Browser::MaybeCreateBackgroundContents(
     content::SiteInstance* source_site_instance,
+    content::RenderFrameHost* opener,
     const GURL& opener_url,
     int32_t route_id,
     int32_t main_frame_route_id,
@@ -2608,7 +2610,7 @@ bool Browser::MaybeCreateBackgroundContents(
   BackgroundContents* contents = nullptr;
   if (allow_js_access) {
     contents = service->CreateBackgroundContents(
-        source_site_instance, route_id, main_frame_route_id,
+        source_site_instance, opener, route_id, main_frame_route_id,
         main_frame_widget_route_id, profile_, frame_name,
         base::ASCIIToUTF16(extension->id()), partition_id,
         session_storage_namespace);
@@ -2620,7 +2622,7 @@ bool Browser::MaybeCreateBackgroundContents(
     contents = service->CreateBackgroundContents(
         content::SiteInstance::Create(
             source_site_instance->GetBrowserContext()),
-        MSG_ROUTING_NONE, MSG_ROUTING_NONE, MSG_ROUTING_NONE, profile_,
+        opener, MSG_ROUTING_NONE, MSG_ROUTING_NONE, MSG_ROUTING_NONE, profile_,

[ncarter (slow), 2017/05/17 20:45:27]

this should be nullptr.

preserving the |opener| here is, I think incorrect: the opener doesn't get a
reference to |contents| -- and I'm pretty sure window.opener in the background
contents' document will be null.

[Łukasz Anforowicz, 2017/05/22 17:19:27]

Good point - the new tests you've suggested would have failed without this. 
Done.

         frame_name, base::ASCIIToUTF16(extension->id()), partition_id,
         session_storage_namespace);