Add IMMEDIATE_CRASH to measure how much V8 APIs return empty MaybeLocal handles

third_party/WebKit/Source/bindings/core/v8/V8BindingMacros.cpp

+// Copyright 2016 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.
+
+#include "wtf/Assertions.h"
+
+namespace blink {
+
+// TODO(haraken): This function was added to investigate how much V8 APIs
+// return empty MaybeLocal handles. Remove this once we finish fixing crbug.com/625512.
+NEVER_INLINE void emptyMaybeHandleReturned()
+{
+    IMMEDIATE_CRASH();
+}
+
+} // namespace blink