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/nsVideoFrame.h

@@ -56,7 +56,7 @@ public:
 
   /* get the size of the video's display */
   nsSize GetVideoIntrinsicSize(nsRenderingContext *aRenderingContext);
-  virtual nsSize GetIntrinsicRatio() override;
+  virtual mozilla::AspectRatio GetIntrinsicRatio() override;
   virtual mozilla::LogicalSize
   ComputeSize(nsRenderingContext *aRenderingContext,
               mozilla::WritingMode aWritingMode,