GrContext single ownership

Author: iskakaushik

shell/platform/darwin/graphics/FlutterDarwinContextMetal.mm

@@ -65,7 +65,8 @@ - (instancetype)initWithMTLDevice:(id<MTLDevice>)device
     // when the GrDirectContext is collected.
     _mainContext = GrDirectContext::MakeMetal(
         (__bridge_retained void*)_device, (__bridge_retained void*)_commandQueue, contextOptions);
-    _resourceContext = _mainContext;
+    _resourceContext = GrDirectContext::MakeMetal(
+        (__bridge_retained void*)_device, (__bridge_retained void*)_commandQueue, contextOptions);
 
     if (!_mainContext || !_resourceContext) {
       FML_DLOG(ERROR) << "Could not create Skia Metal contexts.";