New WebContents created via ctrl-click should be in a new process.

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 1a7e8063626468d6f4ecb99c13cc336d3efca219..507b74a059b8c3d64e34a44a4f7db62a6e60fbe6 100644
--- a/chrome/browser/ui/browser_navigator.cc
+++ b/chrome/browser/ui/browser_navigator.cc
@@ -354,11 +354,16 @@ class ScopedTargetContentsOwner {
 
 content::WebContents* CreateTargetContents(const chrome::NavigateParams& params,
                                            const GURL& url) {
-  WebContents::CreateParams create_params(
-      params.browser->profile(),
-      params.source_site_instance
-          ? params.source_site_instance
-          : tab_util::GetSiteInstanceForNewTab(params.browser->profile(), url));
+  WebContents::CreateParams create_params(params.browser->profile());
+  if (params.use_new_renderer_for_new_contents) {
+    create_params.site_instance = nullptr;

[Charlie Reis, 2017/04/19 20:11:11]

I missed this before, but is there a reason we're not using
GetSiteInstanceForNewTab like below?  That one looks at the destination URL and
creates a SiteInstance in advance in case it's a WebUI or extension URL, so that
we don't immediately have to do a process swap.  For example, I'm curious if a
control click on a web-accessible extension URL (of an extension with a
background page) would first create an empty SiteInstance and then swap to the
extension's existing process.

GetSiteInstanceForNewTab will use a new BrowsingInstance in these cases, so I
think it might be safe to use.  That would basically change the condition here
to:

(params.source_site_instance && !params.use_new_renderer_for_new_contents)
  ? params.source_site_instance
  : tab_util::GetSiteInstanceForNewTab(params.browser->profile(), url));

[Łukasz Anforowicz, 2017/04/20 01:11:29]

Thanks for catching this - you're right this should use
tab_util::GetSiteInstanceForNewTab if possible.

+  } else if (params.source_site_instance) {
+    create_params.site_instance = params.source_site_instance;
+  } else {
+    create_params.site_instance =
+        tab_util::GetSiteInstanceForNewTab(params.browser->profile(), url);
+  }
+
   create_params.main_frame_name = params.frame_name;
   if (params.source_contents) {
     create_params.initial_size =