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/xul/nsImageBoxFrame.cpp

@@ -402,12 +402,13 @@ nsImageBoxFrame::PaintImage(nsRenderingContext& aRenderingContext,
     // Determine dest rect based on intrinsic size & ratio, along with
     // 'object-fit' & 'object-position' properties:
     IntrinsicSize intrinsicSize;
-    nsSize intrinsicRatio;
+    AspectRatio intrinsicRatio;
     if (mIntrinsicSize.width > 0 && mIntrinsicSize.height > 0) {
       // Image has a valid size; use it as intrinsic size & ratio.
       intrinsicSize.width.SetCoordValue(mIntrinsicSize.width);
       intrinsicSize.height.SetCoordValue(mIntrinsicSize.height);
-      intrinsicRatio = mIntrinsicSize;
+      intrinsicRatio =
+          AspectRatio::FromSize(mIntrinsicSize);
     } else {
       // Image doesn't have a (valid) intrinsic size.
       // Try to look up intrinsic ratio and use that at least.