Fix preloadScanner double download issue with link preload and media

third_party/WebKit/Source/core/html/parser/HTMLPreloadScanner.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2009 Torch Mobile, Inc. http://www.torchmobile.com/
  * Copyright (C) 2010 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 187 matching lines @@
             pictureData.sourceSize = m_sourceSize;
             pictureData.picked = true;
         } else if (match(m_tagImpl, imgTag) && !pictureData.sourceURL.isEmpty()) {
             setUrlToLoad(pictureData.sourceURL, AllowURLReplacement);
         }
     }
 
     PassOwnPtr<PreloadRequest> createPreloadRequest(const KURL& predictedBaseURL, const SegmentedString& source, const ClientHintsPreferences& clientHintsPreferences, const PictureData& pictureData, const ReferrerPolicy documentReferrerPolicy)
     {
         PreloadRequest::RequestType requestType = PreloadRequest::RequestTypePreload;
-        if (shouldPreconnect())
+        if (shouldPreconnect()) {
             requestType = PreloadRequest::RequestTypePreconnect;
-        else if (isLinkRelPreload())
+        } else if (!shouldPreload() || !m_matchedMediaAttribute) {
+            return nullptr;
+        }
+
+        if (isLinkRelPreload()) {

[Nate Chapin, 2016/05/17 17:16:55]

Which of these cases really should be mutually exclusive? It seems suspicious
that this patch makes preload and preconnect not mutually exclusive.

[Yoav Weiss, 2016/05/17 21:45:48]

Good point. I changed the conditions to represent the fact that preconnect is
mutual exclusive with link preload as well as regular preload checks.

             requestType = PreloadRequest::RequestTypeLinkRelPreload;
-        else if (!shouldPreload() || !m_matchedMediaAttribute)
-            return nullptr;
+        }
 
         TextPosition position = TextPosition(source.currentLine(), source.currentColumn());
         FetchRequest::ResourceWidth resourceWidth;
         float sourceSize = m_sourceSize;
         bool sourceSizeSet = m_sourceSizeSet;
         if (pictureData.picked) {
             sourceSizeSet = pictureData.sourceSizeSet;
             sourceSize = pictureData.sourceSize;
         }
         if (sourceSizeSet) {
@@ skipping 574 matching lines @@
     ASSERT(document);
     doHtmlPreloadScanning = !document->settings() || document->settings()->doHtmlPreloadScanning();
     doDocumentWritePreloadScanning = doHtmlPreloadScanning && document->frame() && document->frame()->isMainFrame();
     defaultViewportMinWidth = document->viewportDefaultMinWidth();
     viewportMetaZeroValuesQuirk = document->settings() && document->settings()->viewportMetaZeroValuesQuirk();
     viewportMetaEnabled = document->settings() && document->settings()->viewportMetaEnabled();
     referrerPolicy = document->getReferrerPolicy();
 }
 
 } // namespace blink