Add support for `width` based Width Client Hint

Source/core/html/HTMLImageElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
@@ skipping 612 matching lines @@
     ImageResource* image = cachedImage();
     if (!image)
         return FloatSize();
     LayoutSize size;
     size = image->imageSizeForLayoutObject(layoutObject(), 1.0f);
     if (layoutObject() && layoutObject()->isLayoutImage() && image->image() && !image->image()->hasRelativeWidth())
         size.scale(toLayoutImage(layoutObject())->imageDevicePixelRatio());
     return FloatSize(size);
 }
 
+static bool sourceSizeValue(Element& element, Document& currentDocument, float& sourceSize)
+{
+    String sizes = element.fastGetAttribute(sizesAttr);
+    bool exists = !sizes.isNull();
+    if (exists)
+        UseCounter::count(currentDocument, UseCounter::Sizes);
+    sourceSize = SizesAttributeParser(MediaValuesDynamic::create(currentDocument), sizes).length();
+    return exists;
+}
+
+int HTMLImageElement::widthAttributeToInt(const String& value, bool& isValid)
+{
+    // '%' is excluded here since having a width percentage based value means
+    // that the actual width depends on layout, so we cannot use it for resourceWidth.
+    // '*' is exclueded since in Blink and WebKit it means that the entire attribtue is ignored.
+    // TODO(yoav): Count these occurences and try to deprecate/remove if feasible: crbug.com/501870
+    if (!value.isEmpty() && !value.contains('%') && !value.contains('*'))
+        return value.toInt(&isValid);
+
+    isValid = false;
+    return 0;
+}
+
+FetchRequest::ResourceWidth HTMLImageElement::resourceWidth()
+{
+    FetchRequest::ResourceWidth resourceWidth;
+    resourceWidth.isSet = sourceSizeValue(*this, document(), resourceWidth.width);
+    if (!resourceWidth.isSet)
+        resourceWidth.width = widthAttributeToInt(fastGetAttribute(widthAttr), resourceWidth.isSet);
+    return resourceWidth;
+}
+
 float HTMLImageElement::sourceSize(Element& element)
 {
-    String sizes = element.fastGetAttribute(sizesAttr);
-    if (!sizes.isNull())
-        UseCounter::count(document(), UseCounter::Sizes);
-    return SizesAttributeParser(MediaValuesDynamic::create(document()), sizes).length();
+    float value;
+    // We don't care here if the sizes attribute exists, so we ignore the return value.
+    // If it doesn't exist, we just return the default.
+    sourceSizeValue(element, document(), value);
+    return value;
 }
 
 void HTMLImageElement::forceReload() const
 {
     imageLoader().updateFromElement(ImageLoader::UpdateForcedReload);
 }
 
 void HTMLImageElement::selectSourceURL(ImageLoader::UpdateFromElementBehavior behavior)
 {
     if (!document().isActive())
@@ skipping 78 matching lines @@
     ensureUserAgentShadowRoot();
 }
 
 bool HTMLImageElement::isOpaque() const
 {
     Image* image = const_cast<HTMLImageElement*>(this)->imageContents();
     return image && image->currentFrameKnownToBeOpaque();
 }
 
 }