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

test/mjsunit/wasm/wasm-constants.js

Index: test/mjsunit/wasm/wasm-constants.js
diff --git a/test/mjsunit/wasm/wasm-constants.js b/test/mjsunit/wasm/wasm-constants.js
index a064d55aaf8de9a23ad537f18f4c675f94211088..068767bc829e2091b324c5bf2e54702aa4208f9b 100644
--- a/test/mjsunit/wasm/wasm-constants.js
+++ b/test/mjsunit/wasm/wasm-constants.js
@@ -339,22 +339,9 @@ let kTrapMsgs = [
   "invalid index into function table"
 ];
 
+
 function assertTraps(trap, code) {
-    var threwException = true;
-    try {
-      if (typeof code === 'function') {
-        code();
-      } else {
-        eval(code);
-      }
-      threwException = false;
-    } catch (e) {
-      assertEquals("object", typeof e);
-      assertEquals(kTrapMsgs[trap], e.message);
-      // Success.
-      return;
-    }
-    throw new MjsUnitAssertionError("Did not trap, expected: " + kTrapMsgs[trap]);
+  assertThrows(code, WebAssembly.RuntimeError, kTrapMsgs[trap]);
 }
 
 function assertWasmThrows(value, code) {