Fix memory leak in nv12 metal renderer

Bug: webrtc:8308
Change-Id: If6823b2ba7a4a09800bc107985fc52124089277a
Reviewed-on: https://webrtc-review.googlesource.com/4440
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Commit-Queue: Daniela Jovanoska Petrenko <denicija@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20021}
diff --git a/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.mm b/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.mm
index 70ecf54..079b5fb 100644
--- a/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.mm
+++ b/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.mm
@@ -132,4 +132,9 @@
   [renderEncoder setFragmentTexture:_CrCbTexture atIndex:1];
 }
 
+- (void)dealloc {
+  if (_textureCache) {
+    CFRelease(_textureCache);
+  }
+}
 @end