remove locking on JSHostImplementation.CsOwnedObjects

In single-threaded wasm, there is no need to lock since there is only
one caller at a time.

In multi-threaded wasm, the underlying dictionary is thread-static

src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/LegacyExports.cs

@@ -32,18 +32,15 @@ internal static void PreventTrimming()
 
         public static void GetCSOwnedObjectByJSHandleRef(nint jsHandle, int shouldAddInflight, out JSObject? result)
         {
-            lock (JSHostImplementation.s_csOwnedObjects)
+            if (JSHostImplementation.CsOwnedObjects.TryGetValue((int)jsHandle, out WeakReference<JSObject>? reference))
             {
-                if (JSHostImplementation.s_csOwnedObjects.TryGetValue((int)jsHandle, out WeakReference<JSObject>? reference))
+                reference.TryGetTarget(out JSObject? jsObject);
+                if (shouldAddInflight != 0)
                 {
-                    reference.TryGetTarget(out JSObject? jsObject);
-                    if (shouldAddInflight != 0)
-                    {
-                        jsObject?.AddInFlight();
-                    }
-                    result = jsObject;
-                    return;
+                    jsObject?.AddInFlight();
                 }
+                result = jsObject;
+                return;
             }
             result = null;
         }
@@ -77,14 +74,12 @@ public static void CreateCSOwnedProxyRef(nint jsHandle, LegacyHostImplementation
 
             JSObject? res = null;
 
-            lock (JSHostImplementation.s_csOwnedObjects)
+            if (!JSHostImplementation.CsOwnedObjects.TryGetValue((int)jsHandle, out WeakReference<JSObject>? reference) ||
+                !reference.TryGetTarget(out res) ||
+                res.IsDisposed)
             {
-                if (!JSHostImplementation.s_csOwnedObjects.TryGetValue((int)jsHandle, out WeakReference<JSObject>? reference) ||
-                    !reference.TryGetTarget(out res) ||
-                    res.IsDisposed)
-                {
 #pragma warning disable CS0612 // Type or member is obsolete
-                    res = mappedType switch
+                res = mappedType switch
                     {
                         LegacyHostImplementation.MappedType.JSObject => new JSObject(jsHandle),
                         LegacyHostImplementation.MappedType.Array => new Array(jsHandle),
@@ -95,8 +90,7 @@ public static void CreateCSOwnedProxyRef(nint jsHandle, LegacyHostImplementation
                         _ => throw new ArgumentOutOfRangeException(nameof(mappedType))
                     };
 #pragma warning restore CS0612 // Type or member is obsolete
-                    JSHostImplementation.s_csOwnedObjects[(int)jsHandle] = new WeakReference<JSObject>(res, trackResurrection: true);
-                }
+                JSHostImplementation.CsOwnedObjects[(int)jsHandle] = new WeakReference<JSObject>(res, trackResurrection: true);
             }
             if (shouldAddInflight != 0)
             {

src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSHostImplementation.cs

@@ -17,19 +17,18 @@ internal static partial class JSHostImplementation
         // we use this to maintain identity of JSHandle for a JSObject proxy
 #if FEATURE_WASM_THREADS
         [ThreadStatic]
-        private static Dictionary<int, WeakReference<JSObject>>? s_csOwnedObjects_impl;
+#endif
+        private static Dictionary<int, WeakReference<JSObject>>? s_csOwnedObjects;
 
-        public static Dictionary<int, WeakReference<JSObject>> s_csOwnedObjects
+        public static Dictionary<int, WeakReference<JSObject>> CsOwnedObjects
         {
             get
             {
-                s_csOwnedObjects_impl ??= new ();
-                return s_csOwnedObjects_impl;
+                s_csOwnedObjects ??= new ();
+                return s_csOwnedObjects;
             }
         }
-#else
-        public static readonly Dictionary<int, WeakReference<JSObject>> s_csOwnedObjects = new Dictionary<int, WeakReference<JSObject>>();
-#endif
+
         // we use this to maintain identity of GCHandle for a managed object
         public static Dictionary<object, IntPtr> s_gcHandleFromJSOwnedObject = new Dictionary<object, IntPtr>(ReferenceEqualityComparer.Instance);
 
@@ -38,10 +37,7 @@ public static void ReleaseCSOwnedObject(nint jsHandle)
         {
             if (jsHandle != IntPtr.Zero)
             {
-                lock (s_csOwnedObjects)
-                {
-                    s_csOwnedObjects.Remove((int)jsHandle);
-                }
+                CsOwnedObjects.Remove((int)jsHandle);
                 Interop.Runtime.ReleaseCSOwnedObject(jsHandle);
             }
         }
@@ -189,17 +185,14 @@ public static unsafe void FreeMethodSignatureBuffer(JSFunctionBinding signature)
 
         public static JSObject CreateCSOwnedProxy(nint jsHandle)
         {
-            JSObject? res = null;
+            JSObject? res;
 
-            lock (s_csOwnedObjects)
+            if (!CsOwnedObjects.TryGetValue((int)jsHandle, out WeakReference<JSObject>? reference) ||
+                !reference.TryGetTarget(out res) ||
+                res.IsDisposed)
             {
-                if (!s_csOwnedObjects.TryGetValue((int)jsHandle, out WeakReference<JSObject>? reference) ||
-                    !reference.TryGetTarget(out res) ||
-                    res.IsDisposed)
-                {
-                    res = new JSObject(jsHandle);
-                    s_csOwnedObjects[(int)jsHandle] = new WeakReference<JSObject>(res, trackResurrection: true);
-                }
+                res = new JSObject(jsHandle);
+                CsOwnedObjects[(int)jsHandle] = new WeakReference<JSObject>(res, trackResurrection: true);
             }
             return res;
         }

src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Legacy/LegacyHostImplementation.cs

@@ -21,10 +21,7 @@ public static void ReleaseInFlight(object obj)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void RegisterCSOwnedObject(JSObject proxy)
         {
-            lock (JSHostImplementation.s_csOwnedObjects)
-            {
-                JSHostImplementation.s_csOwnedObjects[(int)proxy.JSHandle] = new WeakReference<JSObject>(proxy, trackResurrection: true);
-            }
+            JSHostImplementation.CsOwnedObjects[(int)proxy.JSHandle] = new WeakReference<JSObject>(proxy, trackResurrection: true);
         }
 
         public static MarshalType GetMarshalTypeFromType(Type type)