binding: Changes the association among global-proxy/global/window-instance.

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index 6ef0630d57d2d42711f744f095cd31f58813385e..40eab85e530201454a408673fe3b0a5e38fff8bf 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -5208,6 +5208,10 @@ DocumentNameCollection* Document::documentNamedItems(const AtomicString& name) {
                                                         name);
 }
 
+LocalDOMWindow* Document::defaultView() const {
+  return m_frame ? m_domWindow : nullptr;

[haraken, 2017/02/09 12:46:40]

Would you help me understand why we need to check m_frame?

[Yuki, 2017/02/10 07:47:21]

https://html.spec.whatwg.org/multipage/browsers.html#dom-document-defaultview
The defaultView IDL attribute of the Document interface, on getting, must return
this Document's browsing context's WindowProxy object, if this Document has an
associated browsing context, or null otherwise.

The last phrase "or null otherwise" is important here.  We need to return
nullptr if no |m_frame|.  FYI, we have a layout test, that fails if we ignore
m_frame.

[haraken, 2017/02/10 07:59:40]

I'm wondering why this cannot be 'return m_domWindow'.

It looks like that there's a subtle difference between when m_domWindow is
cleared and when m_frame is cleared, but does it matter here?

[Yuki, 2017/02/10 08:18:19]

I read code a little, and found that
- m_domWindow is cleared by Document::clearDOMWindow
- clearDOMWindow is called only through
  LocalDOMWindow::installNewDocument
  => LocalDOMWindow::clearDocument
     => Document::clearDOMWindow
This doesn't help much to determine if the document is detached from a frame or
not.  Unless the new document is installed, m_domWindow never gets cleared.

[haraken, 2017/02/10 09:15:31]

Makes sense. Can you add a comment about it?

[Yuki, 2017/02/10 11:22:47]

Done.

+}
+
 void Document::finishedParsing() {
   DCHECK(!scriptableDocumentParser() || !m_parser->isParsing());
   DCHECK(!scriptableDocumentParser() || m_readyState != Loading);