Keep normal popups opened from same-origin iframes in an extension process.

content/renderer/render_view.cc

Index: content/renderer/render_view.cc
diff --git a/content/renderer/render_view.cc b/content/renderer/render_view.cc
index e227887f66f1c75d56c31e6e620960d7e287540c..dc259b731282a3e933cc7b675b78a137c6ebdf5f 100644
--- a/content/renderer/render_view.cc
+++ b/content/renderer/render_view.cc
@@ -2149,8 +2149,10 @@ WebNavigationPolicy RenderView::decidePolicyForNavigation(
 
     if (!should_fork) {
       // Give the embedder a chance.
+      bool is_initial_navigation = page_id_ == -1;
       should_fork = content::GetContentClient()->renderer()->ShouldFork(
-          frame, url, is_content_initiated, &send_referrer);
+          frame, url, is_content_initiated, is_initial_navigation,
+          &send_referrer);
     }
 
     if (should_fork) {