Preload scan external CSS for @import

third_party/WebKit/Source/core/fetch/CSSStyleSheetResource.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
@@ skipping 33 matching lines @@
     return toCSSStyleSheetResource(fetcher->requestResource(request, CSSStyleSheetResourceFactory()));
 }
 
 CSSStyleSheetResource* CSSStyleSheetResource::createForTest(const ResourceRequest& request, const String& charset)
 {
     return new CSSStyleSheetResource(request, ResourceLoaderOptions(), charset);
 }
 
 CSSStyleSheetResource::CSSStyleSheetResource(const ResourceRequest& resourceRequest, const ResourceLoaderOptions& options, const String& charset)
     : StyleSheetResource(resourceRequest, CSSStyleSheet, options, "text/css", charset)
+    , m_didNotifyFirstData(false)
 {
 }
 
 CSSStyleSheetResource::~CSSStyleSheetResource()
 {
 }
 
 void CSSStyleSheetResource::setParsedStyleSheetCache(StyleSheetContents* newSheet)
 {
     if (m_parsedStyleSheetCache)
         m_parsedStyleSheetCache->clearReferencedFromResource();
     m_parsedStyleSheetCache = newSheet;
     if (m_parsedStyleSheetCache)
         m_parsedStyleSheetCache->setReferencedFromResource(this);
 }
 
 DEFINE_TRACE(CSSStyleSheetResource)
 {
     visitor->trace(m_parsedStyleSheetCache);
     StyleSheetResource::trace(visitor);
 }
 
 void CSSStyleSheetResource::didAddClient(ResourceClient* c)
 {
     ASSERT(StyleSheetResourceClient::isExpectedType(c));
     // Resource::didAddClient() must be before setCSSStyleSheet(),
     // because setCSSStyleSheet() may cause scripts to be executed, which could destroy 'c' if it is an instance of HTMLLinkElement.
     // see the comment of HTMLLinkElement::setCSSStyleSheet.
     Resource::didAddClient(c);
+    if (m_didNotifyFirstData)
+        static_cast<StyleSheetResourceClient*>(c)->didAppendFirstData(this);

[hiroshige, 2016/07/26 09:57:10]

|*c| must not be destructed during didAppendFirstData() (to prevent similar
issues to crbug.com/612132 (restricted)).

oilpan-reviews, is |*c| kept alive, or should we add
    Persistent<StyleSheetResourceClient> protect = c
?
- |c| points to StyleSheetResourceClient, an on-heap subclass of ResourceClient.
- |c| appears on the C++ stack as an argument of didAddClient() here, but as
ResourceClient*, not as StyleSheetResourceClient*.
- ResourceClient is not on-heap.

[haraken, 2016/07/26 10:01:06]

You won't need Persistent<StyleSheetResourceClient>. Oilpan will keep alive |*c|
on the stack since Oilpan keeps alive all on-stack pointers that exist in the
heap region.

 
     if (!isLoading())

[hiroshige, 2016/07/26 09:57:10]

|c| might be removed as client in didAppendFirstData() in general.
So please check that |c| is still an client, i.e.
    if (hasClient(c) && !isLoading())

[Charlie Harrison, 2016/07/26 16:31:52]

Done.

         static_cast<StyleSheetResourceClient*>(c)->setCSSStyleSheet(m_resourceRequest.url(), m_response.url(), encoding(), this);
 }
 
 const String CSSStyleSheetResource::sheetText(MIMETypeCheck mimeTypeCheck) const
 {
     ASSERT(!isPurgeable());
 
     if (!m_data || m_data->isEmpty() || !canUseSheet(mimeTypeCheck))
         return String();
 
     if (!m_decodedSheetText.isNull())
         return m_decodedSheetText;
 
     // Don't cache the decoded text, regenerating is cheap and it can use quite a bit of memory
     return decodedText();
 }
 
+void CSSStyleSheetResource::appendData(const char* data, size_t length)
+{
+    Resource::appendData(data, length);
+    if (m_didNotifyFirstData)
+        return;
+    ResourceClientWalker<StyleSheetResourceClient> w(clients());
+    while (StyleSheetResourceClient* c = w.next())
+        c->didAppendFirstData(this);
+    m_didNotifyFirstData = true;
+}
+
 void CSSStyleSheetResource::checkNotify()
 {
     // Decode the data to find out the encoding and keep the sheet text around during checkNotify()
     if (m_data)
         m_decodedSheetText = decodedText();
 
     ResourceClientWalker<StyleSheetResourceClient> w(clients());
     while (StyleSheetResourceClient* c = w.next())
         c->setCSSStyleSheet(m_resourceRequest.url(), m_response.url(), encoding(), this);
     // Clear the decoded text as it is unlikely to be needed immediately again and is cheap to regenerate.
@@ skipping 61 matching lines @@
         // This stylesheet resource did conflict with another resource and was
         // not added to the cache.
         setParsedStyleSheetCache(nullptr);
         return;
     }
     setParsedStyleSheetCache(sheet);
     setDecodedSize(m_parsedStyleSheetCache->estimatedSizeInBytes());
 }
 
 } // namespace blink