Bug 1397307 - P1. Make method const. r=gerald

MozReview-Commit-ID: 2UrTZroXpRG

--HG--
extra : rebase_source : d3c95c1c07fb46d28d7aea9fc8891894e7024b5a

dom/media/MediaInfo.h

@@ -297,7 +297,7 @@ public:
     return imageRect;
   }
 
-  Rotation ToSupportedRotation(int32_t aDegree)
+  Rotation ToSupportedRotation(int32_t aDegree) const
   {
     switch (aDegree) {
       case 90: