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

chrome/browser/ui/browser_navigator.cc

Index: chrome/browser/ui/browser_navigator.cc
diff --git a/chrome/browser/ui/browser_navigator.cc b/chrome/browser/ui/browser_navigator.cc
index abf993f818697581907ccd20f65fb0941d6c09be..83ca1d74092de1f23de08defd81766fa7ef02ae6 100644
--- a/chrome/browser/ui/browser_navigator.cc
+++ b/chrome/browser/ui/browser_navigator.cc
@@ -5,6 +5,8 @@
 #include "chrome/browser/ui/browser_navigator.h"
 
 #include <algorithm>
+#include <memory>
+#include <string>
 
 #include "base/command_line.h"
 #include "base/macros.h"
@@ -34,6 +36,8 @@
 #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"
@@ -356,12 +360,24 @@ class ScopedTargetContentsOwner {
 
 content::WebContents* CreateTargetContents(const chrome::NavigateParams& params,
                                            const GURL& url) {
+  // If |params.opener| is present, then (initially) put the new contents in the
+  // same process as the opener.  Note that this is only "initial" placement
+  // (i.e. if subsequent navigation [including the initial navigation] triggers
+  // a cross-process transfer, then the opener and new contents can end up in
+  // separate processes).
+  scoped_refptr<content::SiteInstance> initial_site_instance_for_new_contents =
+      params.opener
+          ? params.opener->GetSiteInstance()
+          : tab_util::GetSiteInstanceForNewTab(params.browser->profile(), url);
+
   WebContents::CreateParams create_params(
-      params.browser->profile(),
-      params.source_site_instance && !params.force_new_process_for_new_contents
-          ? params.source_site_instance
-          : tab_util::GetSiteInstanceForNewTab(params.browser->profile(), url));
+      params.browser->profile(), initial_site_instance_for_new_contents);
   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();
@@ -473,6 +489,7 @@ void Navigate(NavigateParams* params) {
   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();