Implement Object.getNotifier() and remove Object.notify()

src/messages.js

 // Copyright 2012 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 78 matching lines @@
   handler_returned_false:        ["Proxy handler ", "%0", " returned false from '", "%1", "' trap"],
   handler_returned_undefined:    ["Proxy handler ", "%0", " returned undefined from '", "%1", "' trap"],
   proxy_prop_not_configurable:   ["Proxy handler ", "%0", " returned non-configurable descriptor for property '", "%2", "' from '", "%1", "' trap"],
   proxy_non_object_prop_names:   ["Trap '", "%1", "' returned non-object ", "%0"],
   proxy_repeated_prop_name:      ["Trap '", "%1", "' returned repeated property name '", "%2", "'"],
   invalid_weakmap_key:           ["Invalid value used as weak map key"],
   not_date_object:               ["this is not a Date object."],
   observe_non_object:            ["Object.", "%0", " cannot ", "%0", " non-object"],
   observe_non_function:          ["Object.", "%0", " cannot deliver to non-function"],
   observe_callback_frozen:       ["Object.observe cannot deliver to a frozen function object"],
-  observe_type_non_string:       ["Object.notify provided changeRecord with non-string 'type' property"],
+  observe_type_non_string:       ["Invalid changeRecord with non-string 'type' property"],
+  observe_notify_non_notifier:   ["notify called on non-notifier object"],
   // RangeError
   invalid_array_length:          ["Invalid array length"],
   stack_overflow:                ["Maximum call stack size exceeded"],
   invalid_time_value:            ["Invalid time value"],
   // SyntaxError
   unable_to_parse:               ["Parse error"],
   invalid_regexp_flags:          ["Invalid flags supplied to RegExp constructor '", "%0", "'"],
   invalid_regexp:                ["Invalid RegExp pattern /", "%0", "/"],
   illegal_break:                 ["Illegal break statement"],
   illegal_continue:              ["Illegal continue statement"],
@@ skipping 1112 matching lines @@
     throw e;
   }
 }
 
 
 InstallFunctions($Error.prototype, DONT_ENUM, ['toString', ErrorToString]);
 
 // Boilerplate for exceptions for stack overflows. Used from
 // Isolate::StackOverflow().
 var kStackOverflowBoilerplate = MakeRangeError('stack_overflow', []);