Catch uncaught promise rejections from V8 and log to console.

Source/bindings/core/v8/ScriptValueTraits.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ScriptValueTraits_h
+#define ScriptValueTraits_h
+
+#include "bindings/core/v8/ScriptValue.h"
+#include "wtf/HashTraits.h"
+
+namespace blink {
+
+struct ScriptValueHash {
+    static unsigned hash(const ScriptValue& value) { return value.identityHash(); }
+    static bool equal(const ScriptValue& a, const ScriptValue& b) { return a == b; }
+    static const bool safeToCompareToEmptyOrDeleted = true;
+};
+
+struct ScriptValueHashTraits : WTF::SimpleClassHashTraits<ScriptValue> {
+    static const bool hasIsEmptyValueFunction = true;
+    static bool isEmptyValue(const ScriptValue& value) { return value.isEmpty() && !value.isHashTableDeletedValue(); }
+};
+
+} // namespace blink
+
+#endif // !defined(ScriptValueTraits_h)