Add a guard for Node.js

This reverts commit e1b21a0.

src/library_wasm_worker.js

@@ -42,7 +42,11 @@ mergeInto(LibraryManager.library, {
   // Executes a wasm function call received via a postMessage.
   _wasm_worker_runPostMessage: function(e) {
     // Node.js passes the data directly.
-    let data = e.data || e, wasmCall = data['_wsc']; // '_wsc' is short for 'wasm call', trying to use an identifier name that will never conflict with user code
+    let data = e.data
+#if ENVIRONMENT_MAY_BE_NODE
+      || e
+#endif
+      , wasmCall = data['_wsc']; // '_wsc' is short for 'wasm call', trying to use an identifier name that will never conflict with user code
     wasmCall && getWasmTableEntry(wasmCall)(...data['x']);
   },
 

test/code_size/hello_wasm_worker_wasm.js

@@ -9,7 +9,7 @@ function l(a) {
 }
 
 function n(a) {
-    a = a.data || a;
+    a = a.data;
     let d = a._wsc;
     d && f.get(d)(...a.x);
 }

test/code_size/hello_wasm_worker_wasm.json

@@ -1,10 +1,10 @@
 {
   "a.html": 737,
   "a.html.gz": 433,
-  "a.js": 736,
-  "a.js.gz": 465,
+  "a.js": 733,
+  "a.js.gz": 463,
   "a.wasm": 1805,
   "a.wasm.gz": 1002,
-  "total": 3278,
-  "total_gz": 1900
+  "total": 3275,
+  "total_gz": 1898
 }