Move ownership of source SiteInstance to the FrameNavigationEntry.

content/browser/frame_host/frame_navigation_entry.h

Index: content/browser/frame_host/frame_navigation_entry.h
diff --git a/content/browser/frame_host/frame_navigation_entry.h b/content/browser/frame_host/frame_navigation_entry.h
index 256cd266a0f2dab43833c27c717c28ea0689d68b..72ddb8cfdc57699a05bcf561851f64db1541ec66 100644
--- a/content/browser/frame_host/frame_navigation_entry.h
+++ b/content/browser/frame_host/frame_navigation_entry.h
@@ -47,6 +47,7 @@ class CONTENT_EXPORT FrameNavigationEntry
   void UpdateEntry(const std::string& frame_unique_name,
                    int64_t item_sequence_number,
                    int64_t document_sequence_number,
+                   SiteInstanceImpl* source_site_instance,

[dcheng, 2016/05/04 17:01:45]

Random aside: it would be kind of nice if ownership taking parameters were
passed by scoped_refptr. That would make the downcasting quite a bit uglier
though.

[nasko, 2016/05/05 17:51:32]

In this case we won't need to downcast, would we? It is already the Impl type.

                    SiteInstanceImpl* site_instance,

[Charlie Reis, 2016/05/04 23:03:01]

nit: Please list source_site_instance after site_instance, since site_instance
is more important and always present.

[nasko, 2016/05/05 17:51:32]

Done.

                    const GURL& url,
                    const Referrer& referrer,
@@ -86,6 +87,15 @@ class CONTENT_EXPORT FrameNavigationEntry
   }
   SiteInstanceImpl* site_instance() const { return site_instance_.get(); }
 
+  // The |source_site_instance| is used to identify the SiteInstance of the
+  // frame that initiated the navigation.

[Charlie Reis, 2016/05/04 23:03:01]

nit: Let's mention that it is cleared after commit and only present on
renderer-initiated navigations, so people don't assume they can use it
otherwise.

[nasko, 2016/05/05 17:51:32]

Done.

+  void set_source_site_instance(SiteInstanceImpl* source_site_instance) {
+    source_site_instance_ = source_site_instance;
+  }
+  SiteInstanceImpl* source_site_instance() const {
+    return source_site_instance_.get();
+  }
+
   // The actual URL loaded in the frame.  This is in contrast to the virtual
   // URL, which is shown to the user.
   void set_url(const GURL& url) { url_ = url; }
@@ -129,6 +139,9 @@ class CONTENT_EXPORT FrameNavigationEntry
   std::string method_;
   int64_t post_id_;
 
+  // This member is cleared at commit time and not persisted.

[Charlie Reis, 2016/05/04 23:03:01]

nit: and is not

[nasko, 2016/05/05 17:51:32]

Done.

+  scoped_refptr<SiteInstanceImpl> source_site_instance_;
+
   DISALLOW_COPY_AND_ASSIGN(FrameNavigationEntry);
 };