Include stack trace to error message when constructing a new Error with another Error as argument.

src/messages.js

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1119 matching lines @@
         %IgnoreAttributesAndSetProperty(this, 'stack', void 0, DONT_ENUM);
         %IgnoreAttributesAndSetProperty(this, 'arguments', void 0, DONT_ENUM);
         %IgnoreAttributesAndSetProperty(this, 'type', void 0, DONT_ENUM);
         if (m === kAddMessageAccessorsMarker) {
           // DefineOneShotAccessor always inserts a message property and
           // ignores setters.
           DefineOneShotAccessor(this, 'message', function (obj) {
               return FormatMessage(%NewMessageObject(obj.type, obj.arguments));
           });
         } else if (!IS_UNDEFINED(m)) {
-          %IgnoreAttributesAndSetProperty(this,
-                                          'message',
-                                          ToString(m),
-                                          DONT_ENUM);
+          %IgnoreAttributesAndSetProperty(
+              this,
+              'message',
+              (m instanceof $Error) ? m.stack : ToString(m),
+              DONT_ENUM);
         }
         captureStackTrace(this, f);
       } else {
         return new f(m);
       }
     });
     %SetNativeFlag(f);
   }
 
   DefineError(function Error() { });
@@ skipping 53 matching lines @@
     throw e;
   }
 }
 
 
 InstallFunctions($Error.prototype, DONT_ENUM, ['toString', ErrorToString]);
 
 // Boilerplate for exceptions for stack overflows. Used from
 // Isolate::StackOverflow().
 const kStackOverflowBoilerplate = MakeRangeError('stack_overflow', []);