Ensure extensions and the Chrome Web Store are loaded in new BrowsingInstances.

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index e1908ecd0cfaf524fefaf5a55872100f4c988ffa..db7b4173b68299dbe2c50b75fd5bed3ae9e0e094 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -975,6 +975,7 @@ void ChromeContentBrowserClient::SiteInstanceDeleting(
 }
 
 bool ChromeContentBrowserClient::ShouldSwapProcessesForNavigation(
+    SiteInstance* site_instance,
     const GURL& current_url,
     const GURL& new_url) {
   if (current_url.is_empty()) {
@@ -995,6 +996,31 @@ bool ChromeContentBrowserClient::ShouldSwapProcessesForNavigation(
       return true;
   }
 
+  // The checks below only matter if we can retrieve which extensions are
+  // installed.
+  Profile* profile =
+      Profile::FromBrowserContext(site_instance->GetBrowserContext());
+  ExtensionService* service =
+      extensions::ExtensionSystem::Get(profile)->extension_service();
+  if (!service)
+    return false;
+
+  // We must swap if the URL is for an extension and we are not using an
+  // extension process.
+  const Extension* new_extension =
+      service->extensions()->GetExtensionOrAppByURL(ExtensionURLInfo(new_url));
+  // Ignore all hosted apps except the Chrome Web Store, since they do not
+  // require their own BrowsingInstance (e.g., postMessage is ok).
+  if (new_extension &&
+      new_extension->is_hosted_app() &&
+      new_extension->id() != extension_misc::kWebStoreAppId)
+    new_extension = NULL;
+  if (new_extension &&
+      site_instance->HasProcess() &&
+      !service->process_map()->Contains(new_extension->id(),
+                                        site_instance->GetProcess()->GetID()))
+    return true;
+
   return false;
 }