[wasm] Fix asm.js semantics for divide by zero in WASM translation.

test/mjsunit/wasm/asm-wasm-i32.js

 // Copyright 2016 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: --expose-wasm
 
 function WrapInAsmModule(func) {
   function MODULE_NAME(stdlib) {
     "use asm";
     var imul = stdlib.Math.imul;
@@ skipping 195 matching lines @@
   -2147483646,
   -2147483647,
   -2147483648,
   -2147483649,
 ];
 
 var funcs = [
   i32_add,
   i32_sub,
   i32_mul,
-  // TODO(titzer): i32_mul requires Math.imul
-  // TODO(titzer): i32_div divide by zero is incorrect
-  // TODO(titzer): i32_mod by zero is incorrect
+  i32_div,
+  i32_mod,
   i32_and,
   i32_or,
   i32_xor,
   // TODO(titzer): i32_shl on arm
   // TODO(titzer): i32_shr on arm
   // TODO(titzer): i32_sar on arm
   i32_eq,
   i32_ne,
   i32_lt,
   i32_lteq,
@@ skipping 15 matching lines @@
         for (a of inputs) {
           for (b of inputs) {
             assertEquals(func(a, b), module.main(a, b));
           }
         }
       }
     });
   }
 
 })();