Some description changes and documentation for logging.h

ppapi/cpp/module_impl.h

 // Copyright (c) 2010 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.
 
 #ifndef PPAPI_CPP_MODULE_IMPL_H_
 #define PPAPI_CPP_MODULE_IMPL_H_
 
+/// @file
+/// This file defines some simple function templates that help the C++ wrappers
+/// (and are not for external developers to use).
+
 #include "ppapi/cpp/module.h"
 
 namespace pp {
 
 namespace {
 
 // Specialize this function to return the interface string corresponding to the
 // PP?_XXX structure.
 template <typename T> const char* interface_name() {
   return NULL;
 }
 
 template <typename T> inline T const* get_interface() {
   static T const* funcs = reinterpret_cast<T const*>(
       pp::Module::Get()->GetBrowserInterface(interface_name<T>()));
   return funcs;
 }
 
 template <typename T> inline bool has_interface() {
   return get_interface<T>() != NULL;
 }
 
 }  // namespace
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_MODULE_IMPL_H_