[mjsunit] Change assertThrows such that it can check the exception message.

test/mjsunit/wasm/divrem-trap.js

Index: test/mjsunit/wasm/divrem-trap.js
diff --git a/test/mjsunit/wasm/divrem-trap.js b/test/mjsunit/wasm/divrem-trap.js
index 6f3ff5db7369733a7aa8bf667c01ec183c579173..e7452612a36d8bf62aafd7d7d4a99f3a1e305b00 100644
--- a/test/mjsunit/wasm/divrem-trap.js
+++ b/test/mjsunit/wasm/divrem-trap.js
@@ -7,29 +7,6 @@
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
-function assertTraps(code, msg) {
-  var threwException = true;
-  try {
-    if (typeof code === 'function') {
-      code();
-    } else {
-      eval(code);
-    }
-    threwException = false;
-  } catch (e) {
-    if (typeof type_opt === 'function') {
-      assertInstanceof(e, type_opt);
-    }
-    if (arguments.length >= 3) {
-      assertEquals(e.type, cause_opt);
-    }
-    // Success.
-    return;
-  }
-  throw new MjsUnitAssertionError("Did not throw exception");
-}
-
-
 function makeBinop(opcode) {
   var builder = new WasmModuleBuilder();