[test] Check a value type in a test function

Even though IsWasmCompileAllowed function in runtime/runtime-test.cc can
be invoked only when native calls are allowed, so this is not an
actual bug, fuzzing or random testing can call this function and make a
false positive. Thus, add a checking if the given argument is actually
an array buffer.

Bug: v8:5981
Change-Id: I3918c4d68b67a507c93865effa490d7259d63cb1
Reviewed-on: https://chromium-review.googlesource.com/732383Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50116}

src/runtime/runtime-test.cc

@@ -43,8 +43,9 @@ bool IsWasmCompileAllowed(v8::Isolate* isolate, v8::Local<v8::Value> value,
   DCHECK_GT(g_PerIsolateWasmControls.Get().count(isolate), 0);
   const WasmCompileControls& ctrls = g_PerIsolateWasmControls.Get().at(isolate);
   return (is_async && ctrls.AllowAnySizeForAsync) ||
-         (v8::Local<v8::ArrayBuffer>::Cast(value)->ByteLength() <=
-          ctrls.MaxWasmBufferSize);
+         (value->IsArrayBuffer() &&
+          v8::Local<v8::ArrayBuffer>::Cast(value)->ByteLength() <=
+              ctrls.MaxWasmBufferSize);
 }
 
 // Use the compile controls for instantiation, too