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

image/ImageWrapper.cpp

@@ -146,9 +146,9 @@ ImageWrapper::GetIntrinsicSize(nsSize* aSize)
 }
 
 NS_IMETHODIMP
-ImageWrapper::GetIntrinsicRatio(nsSize* aSize)
+ImageWrapper::GetIntrinsicRatio(AspectRatio* aRatio)
 {
-  return mInnerImage->GetIntrinsicRatio(aSize);
+  return mInnerImage->GetIntrinsicRatio(aRatio);
 }
 
 NS_IMETHODIMP_(Orientation)