Convert v8::Value::To* to use MaybeLocal

include/v8config.h

 // Copyright 2013 the V8 project 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 V8CONFIG_H_
 #define V8CONFIG_H_
 
 // Platform headers for feature detection below.
 #if defined(__ANDROID__)
 # include <sys/cdefs.h>
@@ skipping 403 matching lines @@
 #elif V8_HAS___ALIGNOF__
 # define V8_ALIGNOF(type) __alignof__(type)
 #else
 // Note that alignment of a type within a struct can be less than the
 // alignment of the type stand-alone (because of ancient ABIs), so this
 // should only be used as a last resort.
 namespace v8 { template <typename T> class AlignOfHelper { char c; T t; }; }
 # define V8_ALIGNOF(type) (sizeof(::v8::AlignOfHelper<type>) - sizeof(type))
 #endif
 
+// Annotate a function indicating the caller must examine the return value.
+// Use like:
+//   int foo() WARN_UNUSED_RESULT;
+#if V8_HAS_ATTRIBUTE_WARN_UNUSED_RESULT
+#define V8_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
+#else
+#define V8_WARN_UNUSED_RESULT /* NOT SUPPORTED */
+#endif
+
 #endif  // V8CONFIG_H_