Add support for `width` based Width Client Hint

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 18 matching lines @@
 #include "core/html/parser/HTMLPreloadScanner.h"
 
 #include "core/HTMLNames.h"
 #include "core/InputTypeNames.h"
 #include "core/css/MediaList.h"
 #include "core/css/MediaQueryEvaluator.h"
 #include "core/css/MediaValuesCached.h"
 #include "core/css/parser/SizesAttributeParser.h"
 #include "core/dom/Document.h"
 #include "core/frame/Settings.h"
+#include "core/html/HTMLImageElement.h"
 #include "core/html/HTMLMetaElement.h"
 #include "core/html/LinkRelAttribute.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "core/html/parser/HTMLSrcsetParser.h"
 #include "core/html/parser/HTMLTokenizer.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/TraceEvent.h"
 #include "wtf/MainThread.h"
 
 namespace blink {
@@ skipping 61 matching lines @@
 public:
     StartTagScanner(const StringImpl* tagImpl, PassRefPtr<MediaValues> mediaValues)
         : m_tagImpl(tagImpl)
         , m_linkIsStyleSheet(false)
         , m_linkIsPreconnect(false)
         , m_matchedMediaAttribute(true)
         , m_inputIsImage(false)
         , m_sourceSize(0)
         , m_sourceSizeSet(false)
         , m_isCORSEnabled(false)
+        , m_widthValue(0)
+        , m_widthValueSet(false)
+        , m_widthPresent(false)
         , m_defer(FetchRequest::NoDefer)
         , m_allowCredentials(DoNotAllowStoredCredentials)
         , m_mediaValues(mediaValues)
     {
         ASSERT(m_mediaValues->isCached());
         if (match(m_tagImpl, imgTag)
             || match(m_tagImpl, sourceTag)) {
             m_sourceSize = SizesAttributeParser(m_mediaValues, String()).length();
             return;
         }
@@ skipping 43 matching lines @@
         if (shouldPreconnect())
             requestType = PreloadRequest::RequestTypePreconnect;
         else if (!shouldPreload() || !m_matchedMediaAttribute)
             return nullptr;
 
         TextPosition position = TextPosition(source.currentLine(), source.currentColumn());
         FetchRequest::ResourceWidth resourceWidth;
         if (m_sourceSizeSet && m_srcsetImageCandidate.resourceWidth() != UninitializedDescriptor) {
             resourceWidth.width = m_sourceSize;
             resourceWidth.isSet = true;
+        } else {
+            resourceWidth.isSet = m_widthValueSet;
+            resourceWidth.width = m_widthValue;

[Mike West, 2015/06/18 06:20:04]

Nit: The `if` part of the clause reverses the order of the assignment.

[Yoav Weiss, 2015/06/18 06:30:22]

I'll reverse it

         }
+
         OwnPtr<PreloadRequest> request = PreloadRequest::create(initiatorFor(m_tagImpl), position, m_urlToLoad, predictedBaseURL, resourceType(), resourceWidth, clientHintsPreferences, requestType);
         if (isCORSEnabled())
             request->setCrossOriginEnabled(allowStoredCredentials());
         request->setCharset(charset());
         request->setDefer(m_defer);
         return request.release();
     }
 
 private:
     template<typename NameType>
@@ skipping 22 matching lines @@
             m_srcsetAttributeValue = attributeValue;
             m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), m_sourceSize, attributeValue);
             setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), m_sourceSize, m_imgSrcUrl, m_srcsetImageCandidate), AllowURLReplacement);
         } else if (match(attributeName, sizesAttr) && !m_sourceSizeSet) {
             m_sourceSize = SizesAttributeParser(m_mediaValues, attributeValue).length();
             m_sourceSizeSet = true;
             if (!m_srcsetImageCandidate.isEmpty()) {
                 m_srcsetImageCandidate = bestFitSourceForSrcsetAttribute(m_mediaValues->devicePixelRatio(), m_sourceSize, m_srcsetAttributeValue);
                 setUrlToLoad(bestFitSourceForImageAttributes(m_mediaValues->devicePixelRatio(), m_sourceSize, m_imgSrcUrl, m_srcsetImageCandidate), AllowURLReplacement);
             }
+        } else if (match(attributeName, widthAttr) && !m_widthPresent) {

[Mike West, 2015/06/18 06:20:04]

Could you drop the `widthPresent` property in favor of just checking
`m_widthValueSet` as we do with other attributes above?

[Yoav Weiss, 2015/06/18 06:30:22]

I did, but there was a bug there in cases like `<img src=foo width="500%"
width="100">`.
Once we've seen width, even if the value is not a valid one (which we ignore),
we should ignore following `width` attributes.

[Mike West, 2015/06/18 06:34:35]

Hrm. Isn't that the opposite of how the parser works? Don't we overwrite the
value of `element.width` with the final value set?

+            m_widthPresent = true;
+            m_widthValue = HTMLImageElement::widthAttributeToInt(attributeValue, m_widthValueSet);
         }
     }
 
     template<typename NameType>
     void processLinkAttribute(const NameType& attributeName, const String& attributeValue)
     {
         // FIXME - Don't set rel/media/crossorigin multiple times.
         if (match(attributeName, hrefAttr)) {
             setUrlToLoad(attributeValue, DisallowURLReplacement);
         } else if (match(attributeName, relAttr)) {
@@ skipping 147 matching lines @@
     String m_charset;
     bool m_linkIsStyleSheet;
     bool m_linkIsPreconnect;
     bool m_matchedMediaAttribute;
     bool m_inputIsImage;
     String m_imgSrcUrl;
     String m_srcsetAttributeValue;
     float m_sourceSize;
     bool m_sourceSizeSet;
     bool m_isCORSEnabled;
+    int m_widthValue;
+    bool m_widthValueSet;
+    bool m_widthPresent;
     FetchRequest::DeferOption m_defer;
     StoredCredentials m_allowCredentials;
     RefPtr<MediaValues> m_mediaValues;
 };
 
 TokenPreloadScanner::TokenPreloadScanner(const KURL& documentURL, PassOwnPtr<CachedDocumentParameters> documentParameters)
     : m_documentURL(documentURL)
     , m_inStyle(false)
     , m_inPicture(false)
     , m_isAppCacheEnabled(false)
@@ skipping 206 matching lines @@
         mediaValues = givenMediaValues;
     else
         mediaValues = MediaValuesCached::create(*document);
     ASSERT(mediaValues->isSafeToSendToAnotherThread());
     defaultViewportMinWidth = document->viewportDefaultMinWidth();
     viewportMetaZeroValuesQuirk = document->settings() && document->settings()->viewportMetaZeroValuesQuirk();
     viewportMetaEnabled = document->settings() && document->settings()->viewportMetaEnabled();
 }
 
 }