Issue #1619 - Convert Intrinsic Ratio to Float

https://bugzilla.mozilla.org/show_bug.cgi?id=1547792

Aspect Ratio handling simplified by using floating point integers:
- Multiplication of value (or inverse value) to a known side for Scaling
- No unequal equal values such as "4/3" vs "8/6" vs "20/15"
- Truly "Empty" aspect ratios, even if one dimension is not 0

layout/base/nsLayoutUtils.h

@@ -65,6 +65,7 @@ struct nsStyleImageOrientation;
 struct nsOverflowAreas;
 
 namespace mozilla {
+struct aspectRatio;
 enum class CSSPseudoElementType : uint8_t;
 class EventListenerManager;
 class SVGImageContext;
@@ -126,6 +127,7 @@ enum class RelativeTo {
  */
 class nsLayoutUtils
 {
+  typedef mozilla::AspectRatio AspectRatio;
   typedef mozilla::dom::DOMRectList DOMRectList;
   typedef mozilla::layers::Layer Layer;
   typedef mozilla::ContainerLayerParameters ContainerLayerParameters;
@@ -1217,7 +1219,7 @@ public:
    */
   static nsRect ComputeObjectDestRect(const nsRect& aConstraintRect,
                                       const IntrinsicSize& aIntrinsicSize,
-                                      const nsSize& aIntrinsicRatio,
+                                      const AspectRatio& aIntrinsicRatio,
                                       const nsStylePosition* aStylePos,
                                       nsPoint* aAnchorPoint = nullptr);
 
@@ -1837,7 +1839,7 @@ public:
    */
   static void ComputeSizeForDrawing(imgIContainer* aImage,
                                     CSSIntSize&    aImageSize,
-                                    nsSize&        aIntrinsicRatio,
+                                    AspectRatio&        aIntrinsicRatio,
                                     bool&          aGotWidth,
                                     bool&          aGotHeight);