Bug 1583980 - Restrict mapping of width and height to aspect-ratio for <img> for now. r=bzbarsky

This is an easier thing to implement interoperably than what we implement now,
which is basically "whatever goes through this function".

Differential Revision: https://phabricator.services.mozilla.com/D47145

--HG--
extra : moz-landing-system : lando

dom/html/HTMLImageElement.cpp

@@ -234,11 +234,11 @@ bool HTMLImageElement::ParseAttribute(int32_t aNamespaceID, nsAtom* aAttribute,
 
 void HTMLImageElement::MapAttributesIntoRule(
     const nsMappedAttributes* aAttributes, MappedDeclarations& aDecls) {
-  nsGenericHTMLElement::MapImageAlignAttributeInto(aAttributes, aDecls);
-  nsGenericHTMLElement::MapImageBorderAttributeInto(aAttributes, aDecls);
-  nsGenericHTMLElement::MapImageMarginAttributeInto(aAttributes, aDecls);
-  nsGenericHTMLElement::MapImageSizeAttributesInto(aAttributes, aDecls);
-  nsGenericHTMLElement::MapCommonAttributesInto(aAttributes, aDecls);
+  MapImageAlignAttributeInto(aAttributes, aDecls);
+  MapImageBorderAttributeInto(aAttributes, aDecls);
+  MapImageMarginAttributeInto(aAttributes, aDecls);
+  MapImageSizeAttributesInto(aAttributes, aDecls, MapAspectRatio::Yes);
+  MapCommonAttributesInto(aAttributes, aDecls);
 }
 
 nsChangeHint HTMLImageElement::GetAttributeChangeHint(const nsAtom* aAttribute,

dom/html/nsGenericHTMLElement.cpp

@@ -1220,7 +1220,8 @@ void nsGenericHTMLElement::MapHeightAttributeInto(
 }
 
 void nsGenericHTMLElement::MapImageSizeAttributesInto(
-    const nsMappedAttributes* aAttributes, MappedDeclarations& aDecls) {
+    const nsMappedAttributes* aAttributes, MappedDeclarations& aDecls,
+    MapAspectRatio aMapAspectRatio) {
   auto* width = aAttributes->GetAttr(nsGkAtoms::width);
   auto* height = aAttributes->GetAttr(nsGkAtoms::height);
   if (width) {
@@ -1229,11 +1230,8 @@ void nsGenericHTMLElement::MapImageSizeAttributesInto(
   if (height) {
     MapDimensionAttributeInto(aDecls, eCSSProperty_height, *height);
   }
-  // NOTE(emilio): If we implement the unrestricted aspect-ratio proposal, we
-  // probably need to make this attribute mapping not apply to things like
-  // <marquee> and <table>, which right now can go through this path.
   if (StaticPrefs::layout_css_width_and_height_map_to_aspect_ratio_enabled() &&
-      width && height) {
+      aMapAspectRatio == MapAspectRatio::Yes && width && height) {
     Maybe<double> w;
     if (width->Type() == nsAttrValue::eInteger) {
       w.emplace(width->GetIntegerValue());

dom/html/nsGenericHTMLElement.h

@@ -482,15 +482,16 @@ class nsGenericHTMLElement : public nsGenericHTMLElementBase {
    */
   static void MapImageMarginAttributeInto(const nsMappedAttributes* aAttributes,
                                           mozilla::MappedDeclarations&);
+
+  // Whether to map the width and height attributes to aspect-ratio.
+  enum class MapAspectRatio { No, Yes };
+
   /**
    * Helper to map the image position attribute into a style struct.
-   *
-   * @param aAttributes the list of attributes to map
-   * @param aData the returned rule data [INOUT]
-   * @see GetAttributeMappingFunction
    */
-  static void MapImageSizeAttributesInto(const nsMappedAttributes* aAttributes,
-                                         mozilla::MappedDeclarations&);
+  static void MapImageSizeAttributesInto(const nsMappedAttributes*,
+                                         mozilla::MappedDeclarations&,
+                                         MapAspectRatio = MapAspectRatio::No);
 
   /**
    * Helper to map `width` attribute into a style struct.