Bug 1398659. P11 - replace mCacheStream.GetLength() with GetLength(). r=gerald

MozReview-Commit-ID: BGgObe2XG5C

--HG--
extra : rebase_source : a9dddd16ca071cef11a4546b5f9bc649b6e47e5b
extra : source : 100d0443ff9cab14ddc17eba13d824ff2b2bbef5

dom/media/MediaResource.cpp

@@ -748,7 +748,7 @@ void ChannelMediaResource::Resume()
       mReopenOnError = true;
       element->DownloadResumed();
     } else {
-      int64_t totalLength = mCacheStream.GetLength();
+      int64_t totalLength = GetLength();
       // If mOffset is at the end of the stream, then we shouldn't try to
       // seek to it. The seek will fail and be wasted anyway. We can leave
       // the channel dead; if the media cache wants to read some other data