Remove uses of const in distiller javascript

components/dom_distiller/core/javascript/dom_distiller_viewer.js

Index: components/dom_distiller/core/javascript/dom_distiller_viewer.js
diff --git a/components/dom_distiller/core/javascript/dom_distiller_viewer.js b/components/dom_distiller/core/javascript/dom_distiller_viewer.js
index 4122dc7c0de0bc04ebe78409fb955ea4c784f028..4a80bba65d38d28c1aba4551d05cf11e7e575149 100644
--- a/components/dom_distiller/core/javascript/dom_distiller_viewer.js
+++ b/components/dom_distiller/core/javascript/dom_distiller_viewer.js
@@ -204,8 +204,8 @@ var pincher = (function() {
   var shiftY;
 
   // The zooming speed relative to pinching speed.
-  const FONT_SCALE_MULTIPLIER = 0.5;
-  const MIN_SPAN_LENGTH = 20;
+  var FONT_SCALE_MULTIPLIER = 0.5;
+  var MIN_SPAN_LENGTH = 20;
 
   // The font size is guaranteed to be in px.
   var baseSize =