Add "frame to navigate" to NavigationEntry and plumb it to the RenderViewImpl

content/public/browser/navigation_entry.h

Index: content/public/browser/navigation_entry.h
diff --git a/content/public/browser/navigation_entry.h b/content/public/browser/navigation_entry.h
index 63af6871b20e202b7d796960e9d298c9d86e2a35..cc25a254cf08c2904dc5aa10e5b09122a70f481f 100644
--- a/content/public/browser/navigation_entry.h
+++ b/content/public/browser/navigation_entry.h
@@ -182,6 +182,12 @@ class NavigationEntry {
   // resources.
   virtual void SetCanLoadLocalResources(bool allow) = 0;
   virtual bool GetCanLoadLocalResources() const = 0;
+
+  // Used to specify which frame to navigate. If empty, the main frame is
+  // navigated. This is currently not persisted in session restore, because it
+  // is currently only used in tests.
+  virtual void SetFrameToNavigate(const std::string& frame_name) = 0;
+  virtual const std::string& GetFrameToNavigate() const = 0;
 };
 
 }  // namespace content