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

src/wasm/wasm-module.cc

Index: src/wasm/wasm-module.cc
diff --git a/src/wasm/wasm-module.cc b/src/wasm/wasm-module.cc
index 2e36978440e326751a7e9348377bd0e76b186469..4d8b60fdf2269b302d6992c4cd165e1b5a7fb5e1 100644
--- a/src/wasm/wasm-module.cc
+++ b/src/wasm/wasm-module.cc
@@ -1658,6 +1658,9 @@ class WasmInstanceBuilder {
           break;
         }
         case kExternalMemory: {
+          // Validation should have failed if more than one memory object was
+          // provided.
+          DCHECK(!instance->has_memory_object());
           if (!WasmJs::IsWasmMemoryObject(isolate_, value)) {
             ReportLinkError("memory import must be a WebAssembly.Memory object",
                             index, module_name, import_name);