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

src/wasm/wasm-js.cc

Index: src/wasm/wasm-js.cc
diff --git a/src/wasm/wasm-js.cc b/src/wasm/wasm-js.cc
index 6dc14952a01e943b8bd5a9fc012c8d648c59dbae..bcccf2e3ebcd4a10c454392f5b1530a9405a2ef1 100644
--- a/src/wasm/wasm-js.cc
+++ b/src/wasm/wasm-js.cc
@@ -141,6 +141,11 @@ v8::internal::wasm::ZoneBuffer* TranslateAsmModule(
     return nullptr;
   }
 
+  if (!info->scope()->declarations()->at(0)->IsFunctionDeclaration()) {
+    thrower->Error("Asm.js validation failed: non-function declaration");
+    return nullptr;
+  }
+
   info->set_literal(
       info->scope()->declarations()->at(0)->AsFunctionDeclaration()->fun());