--- a/dom/media/MediaInfo.h
+++ b/dom/media/MediaInfo.h
@@ -292,17 +292,17 @@ public:
     gfx::IntRect imageRect = ImageRect();
     imageRect.x = (imageRect.x * aWidth) / mImage.width;
     imageRect.y = (imageRect.y * aHeight) / mImage.height;
     imageRect.SetWidth((aWidth * imageRect.Width()) / mImage.width);
     imageRect.SetHeight((aHeight * imageRect.Height()) / mImage.height);
     return imageRect;
   }
 
-  Rotation ToSupportedRotation(int32_t aDegree)
+  Rotation ToSupportedRotation(int32_t aDegree) const
   {
     switch (aDegree) {
       case 90:
         return kDegree_90;
       case 180:
         return kDegree_180;
       case 270:
         return kDegree_270;