[wasm][asm.js] Allow a function to be exported more than once.

test/mjsunit/wasm/asm-wasm.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --validate-asm --allow-natives-syntax
 
 var stdlib = this;
 
 function assertValidAsm(func) {
   assertTrue(%IsAsmWasmCode(func));
@@ skipping 1657 matching lines @@
   var foo = fround(1.25);
   function caller() {
     foo = fround(foo + fround(1.0));
     foo = fround(foo + fround(1.0));
     return +foo;
   }
   return {caller: caller};
 }
 
 assertWasm(3.25, TestFloatGlobals);
+
+
+(function TestExportTwice() {
+  function asmModule() {
+    "use asm";
+    function foo() {
+      return 42;
+    }
+    return {bar: foo, baz: foo};
+  }
+  var m = asmModule();
+  assertEquals(42, m.bar());
+  assertEquals(42, m.baz());
+})();