Bug 1369322 - MediaResourceIndex follows ShouldCacheReads recommendation - r=cpearce

MozReview-Commit-ID: A8mtz2fJd71

--HG--
extra : rebase_source : 81949d559c5482951ed9186c92d0759dd4a6b3b0

dom/media/MediaResource.h

@@ -747,7 +747,9 @@ public:
   explicit MediaResourceIndex(MediaResource* aResource)
     : mResource(aResource)
     , mOffset(0)
-    , mCacheBlockSize(SelectCacheSize(MediaPrefs::MediaResourceIndexCache()))
+    , mCacheBlockSize(aResource->ShouldCacheReads()
+                      ? SelectCacheSize(MediaPrefs::MediaResourceIndexCache())
+                      : 0 )
     , mCachedOffset(0)
     , mCachedBytes(0)
     , mCachedBlock(MakeUnique<char[]>(mCacheBlockSize))