Adjust wasm_serialization_tests.html the layout test to expect null on failure.

third_party/WebKit/LayoutTests/http/tests/wasm/wasm_serialization_tests.js

Index: third_party/WebKit/LayoutTests/http/tests/wasm/wasm_serialization_tests.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/wasm/wasm_serialization_tests.js b/third_party/WebKit/LayoutTests/http/tests/wasm/wasm_serialization_tests.js
index ab4e4d383e18ef64c1cb1814c20017d128716a47..940063187472217b7fd8e69c2f84e8aa32707cec 100644
--- a/third_party/WebKit/LayoutTests/http/tests/wasm/wasm_serialization_tests.js
+++ b/third_party/WebKit/LayoutTests/http/tests/wasm/wasm_serialization_tests.js
@@ -57,12 +57,7 @@ function TestIncompatibleDowngrade() {
       assert_true(invalidated,
                   "the serialized blob should contain some non-null bytes.");
 
-      var deserialized = undefined;
-      try {
-        deserialized = window.internals.deserializeBuffer(byteView.buffer);
-        assert_unreached();
-      } catch (e) {
-        assert_equals(deserialized, undefined);
-      }
+      var deserialized = window.internals.deserializeBuffer(byteView.buffer);
+      assert_equals(deserialized, null);
     });
 }