[wasm] Require wasm explicit asm instantiation to be of a function.

test/mjsunit/wasm/asm-wasm.js

Index: test/mjsunit/wasm/asm-wasm.js
diff --git a/test/mjsunit/wasm/asm-wasm.js b/test/mjsunit/wasm/asm-wasm.js
index 4c28b619c306b9b6691e3a8e2a189a372a37de69..4391e039ebfb977a24f31ef7802a3abb36ed423d 100644
--- a/test/mjsunit/wasm/asm-wasm.js
+++ b/test/mjsunit/wasm/asm-wasm.js
@@ -1530,3 +1530,15 @@ assertWasm(1, TestXor);
   assertEquals(0x80000000, wasm.u0x80000000());
   assertEquals(0x87654321, wasm.u0x87654321());
 })();
+
+(function TestBadNoDeclaration() {
+  assertThrows(function() {
+    Wasm.instantiateModuleFromAsm('33;');
+  });
+})();
+
+(function TestBadVarDeclaration() {
+  assertThrows(function() {
+    Wasm.instantiateModuleFromAsm('var x = 3;');
+  });
+})();