Merge pull request #765 from youennf/export-clone-videoframe

Export clone video frame algorithm as it is useful in other specs

Author: Djuffin

index.src.html

@@ -4007,7 +4007,7 @@
             |heightScale| and round the result. Assign the rounded result to
             |frame|'s {{VideoFrame/[[display height]]}}.
 
-: <dfn>Clone VideoFrame</dfn> (with |frame|)
+: <dfn export>Clone VideoFrame</dfn> (with |frame|)
 :: 1. Let |clone| be a new {{VideoFrame}} initialized as follows:
         1. Let |resource| be the [=media resource=] referenced by |frame|’s
             [[resource reference]].