Catch uncaught promise rejections from V8 and log to console.

Source/bindings/core/v8/ScriptValueTraits.h

Index: Source/bindings/core/v8/ScriptValueTraits.h
diff --git a/Source/bindings/core/v8/ScriptValueTraits.h b/Source/bindings/core/v8/ScriptValueTraits.h
new file mode 100644
index 0000000000000000000000000000000000000000..19b7e1ef8886d9c8dfc3becdf0fd052b4cea3fe2
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+++ b/Source/bindings/core/v8/ScriptValueTraits.h
@@ -0,0 +1,26 @@
+// 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)