Clarify some details of global objects implementation.

include/v8.h

 // Copyright 2007-2009 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 3035 matching lines @@
   const char** names_;
 };
 
 
 /**
  * A sandboxed execution context with its own set of built-in objects
  * and functions.
  */
 class V8EXPORT Context {
  public:
-  /** Returns the global object of the context. */
+  /**
+   * Returns the global proxy object.
+   *
+   * Global proxy object is a thin wrapper whose prototype points to
+   * actual context's global object with the properties like Object, etc.
+   * This is done that way for security reasons (for more details see
+   * https://wiki.mozilla.org/Gecko:SplitWindow).
+   *
+   * Please note that changes to global proxy object prototype most probably
+   * would break VM---v8 expects only global object as a prototype of
+   * global proxy object.
+   */
   Local<Object> Global();
 
   /**
    * Detaches the global object from its context before
    * the global object can be reused to create a new context.
    */
   void DetachGlobal();
 
   /**
    * Reattaches a global object to a context.  This can be used to
@@ skipping 756 matching lines @@
 
 
 }  // namespace v8
 
 
 #undef V8EXPORT
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_