Add support for `width` based Width Client Hint

Source/core/html/HTMLImageElement.cpp

Index: Source/core/html/HTMLImageElement.cpp
diff --git a/Source/core/html/HTMLImageElement.cpp b/Source/core/html/HTMLImageElement.cpp
index d46f9de78aee086b9d05ce96120bbe88d13633ad..9c311dd6a524415b5fa7b598a960d8cf0e625206 100644
--- a/Source/core/html/HTMLImageElement.cpp
+++ b/Source/core/html/HTMLImageElement.cpp
@@ -402,6 +402,7 @@ int HTMLImageElement::width(bool ignorePendingStylesheets)
     if (!layoutObject()) {
         // check the attribute first for an explicit pixel value
         bool ok;
+        // TODO(yoav): That seems buggy when width is provided with a '%'.

[igrigorik, 2015/06/17 17:26:28]

Per spec, it's CSS px only:
http://www.w3.org/html/wg/drafts/html/master/semantics.html#attr-dim-width

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

Is there a bug we could point to here?

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

I'll open one, once I make sure this is an actual issue.

[Yoav Weiss, 2015/06/18 09:19:27]

Seems to be returning the calculated width after layout and 0 before layout,
which makes sense: http://jsbin.com/bijirekazu/edit?html,console,output
I'll delete the comment.

         int width = getAttribute(widthAttr).toInt(&ok);
         if (ok)
             return width;
@@ -630,12 +631,41 @@ FloatSize HTMLImageElement::defaultDestinationSize() const
     return FloatSize(size);
 }
 
-float HTMLImageElement::sourceSize(Element& element)
+static bool sourceSizeValue(Element& element, Document& currentDocument, float& sourceSize)
 {
     String sizes = element.fastGetAttribute(sizesAttr);
-    if (!sizes.isNull())
-        UseCounter::count(document(), UseCounter::Sizes);
-    return SizesAttributeParser(MediaValuesDynamic::create(document()), sizes).length();
+    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)
+{
+    if (!value.isEmpty() && !value.contains('%') && !value.contains('*'))

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

Nit: Could you add a comment here explaining why you're excluding '%' and '*'?

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

Will do

+        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)
+{
+    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