fix the return of odd numbered pixels

The point of subtracting a dimension%2 from its actual dimension is to
avoid odd numbered pixels, so due to variation of DPR from device to
device the subtraction should be done at the end of pixel calculation.

addons/gst-web/src/input.js

@@ -535,8 +535,8 @@ class Input {
 
     getWindowResolution() {
         return [
-            parseInt((document.body.offsetWidth - document.body.offsetWidth%2) * window.devicePixelRatio),
-            parseInt((document.body.offsetHeight - document.body.offsetHeight%2) * window.devicePixelRatio)
+            parseInt( (() => {var width = document.body.offsetWidth * window.devicePixelRatio; return width - width % 2})() ),
+            parseInt( (() => {var height = document.body.offsetHeight * window.devicePixelRatio; return height - height % 2})() )
         ];
     }
 }