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/generic/nsSubDocumentFrame.cpp

@@ -671,7 +671,7 @@ nsSubDocumentFrame::GetIntrinsicSize()
   return nsAtomicContainerFrame::GetIntrinsicSize();
 }
 
-/* virtual */ nsSize
+/* virtual */ AspectRatio
 nsSubDocumentFrame::GetIntrinsicRatio()
 {
   nsIFrame* subDocRoot = ObtainIntrinsicSizeFrame();
@@ -771,7 +771,7 @@ nsSubDocumentFrame::Reflow(nsPresContext*           aPresContext,
     // Size & position the view according to 'object-fit' & 'object-position'.
     nsIFrame* subDocRoot = ObtainIntrinsicSizeFrame();
     IntrinsicSize intrinsSize;
-    nsSize intrinsRatio;
+    AspectRatio intrinsRatio;
     if (subDocRoot) {
       intrinsSize = subDocRoot->GetIntrinsicSize();
       intrinsRatio = subDocRoot->GetIntrinsicRatio();