HTML Imports: Make sure new imports being added to the "first child"

Source/core/html/imports/HTMLImportChild.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 196 matching lines @@
     m_client = 0;
 }
 
 HTMLLinkElement* HTMLImportChild::link() const
 {
     if (!m_client)
         return 0;
     return m_client->link();
 }
 
+// Ensuring following invariants against the import tree:
+// - HTMLImportChild::firstImport() is the "first import" of the DFS order of the import tree.
+// - The "first import" manages all the children that is loaded by the document.
+void HTMLImportChild::normalize()

[dglazkov, 2014/05/12 17:32:37]

I apologize, I am trying to (re)learn how this works.

normalize() is invoked in addImport, which itself comes from createLoader or
shareLoader, which in turn comes from ensureLoader. This is where I get lost.
The ensureLoader is called in several places, and all of them have to do with
loading completion or start.

I am not sure I understand why. Can't the ordering be ensured at the time the
link is processed? Please help me understand :)

+{
+    if (!loader()->isFirstImport(this) && this->precedes(loader()->firstImport())) {
+        HTMLImportChild* oldFirst = loader()->firstImport();
+        loader()->moveToFirst(this);
+        takeChildrenFrom(oldFirst);
+    }
+
+    for (HTMLImport* child = firstChild(); child; child = child->next())
+        toHTMLImportChild(child)->normalize();
+}
+
 #if !defined(NDEBUG)
 void HTMLImportChild::showThis()
 {
+    bool isFirst = loader() ? loader()->isFirstImport(this) : false;
     HTMLImport::showThis();
-    fprintf(stderr, " loader=%p step=%p sync=%s url=%s",
+    fprintf(stderr, " loader=%p first=%d, step=%p sync=%s url=%s",
         m_loader,
+        isFirst,
         m_customElementMicrotaskStep.get(),
         isSync() ? "Y" : "N",
         url().string().utf8().data());
 }
 #endif
 
 } // namespace WebCore