[wasm] JS API tests for `WebAssembly.validate`

src/wasm/module-decoder.cc

Index: src/wasm/module-decoder.cc
diff --git a/src/wasm/module-decoder.cc b/src/wasm/module-decoder.cc
index 506c7355ab62fca4a9bea16aa0d62a6621b46034..8f92c6e34cf28de44777fd1961df40c08d16f9fb 100644
--- a/src/wasm/module-decoder.cc
+++ b/src/wasm/module-decoder.cc
@@ -324,7 +324,11 @@ class ModuleDecoder : public Decoder {
                                      &module->min_mem_pages, &has_max,
                                      kSpecMaxWasmMemoryPages,
                                      &module->max_mem_pages);
-            module->has_memory = true;
+            if (module->has_memory) {
+              error("At most one memory object is supported");
+            } else {
+              module->has_memory = true;
+            }
             break;
           }
           case kExternalGlobal: {