Track frame openers in FrameTreeNodes instead of WebContents

content/test/test_web_contents.h

Index: content/test/test_web_contents.h
diff --git a/content/test/test_web_contents.h b/content/test/test_web_contents.h
index 53bc82a04ea80a42cb5fd92bd07e073e0aa2c759..edc6dd946330aec86dc0bb40dbdaf003c2848421 100644
--- a/content/test/test_web_contents.h
+++ b/content/test/test_web_contents.h
@@ -77,7 +77,8 @@ class TestWebContents : public WebContentsImpl, public WebContentsTester {
     delegate_view_override_ = view;
   }
 
-  // Allows us to simulate this tab having an opener.
+  // Allows us to simulate this tab's main frame having an opener that points
+  // to the main frame of the |opener|.
   void SetOpener(TestWebContents* opener);
 
   // Allows us to simulate that a contents was created via CreateNewWindow.