[wasm][asm.js] Require exported asm.js functions have be names.

The asm.js spec requires exports to be identifiers,
this was DCHECKED in the asm-wasm-builder, but not the typer.

BUG=672046
R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2552913004
Cr-Commit-Position: refs/heads/master@{#41557}

src/asmjs/asm-typer.cc

@@ -935,6 +935,10 @@ AsmType* AsmTyper::ValidateExport(ReturnStatement* exports) {
              "Only normal object properties may be used in the export object "
              "literal.");
       }
+      if (!prop->key()->AsLiteral()->IsPropertyName()) {
+        FAIL(prop->key(),
+             "Exported functions must have valid identifier names.");
+      }
 
       auto* export_obj = prop->value()->AsVariableProxy();
       if (export_obj == nullptr) {

test/mjsunit/wasm/asm-wasm.js

@@ -1484,6 +1484,19 @@ assertWasm(-34359738370.75, TestNegativeDouble);
 })();
 
 
+(function TestBadExportKey() {
+  function Module() {
+    "use asm";
+    function func() {
+    }
+    return {123: func};
+  }
+
+  Module(stdlib);
+  assertTrue(%IsNotAsmWasmCode(Module));
+})();
+
+
 function TestAndIntAndHeapValue(stdlib, foreign, buffer) {
   "use asm";
   var HEAP32 = new stdlib.Int32Array(buffer);