Linux: fix a bunch of NULL vs. 0 issues spotted by gcc 4.5.

chrome/common/plugin_messages.cc

 // 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.
 
 #include "base/utf_string_conversions.h"
 #include "ipc/ipc_channel_handle.h"
 
 #define IPC_MESSAGE_IMPL
 #include "chrome/common/plugin_messages.h"
 
@@ skipping 39 matching lines @@
       double_value(0),
       npobject_routing_id(-1) {
 }
 
 NPVariant_Param::~NPVariant_Param() {
 }
 
 PluginMsg_UpdateGeometry_Param::PluginMsg_UpdateGeometry_Param()
     : transparent(false),
 #if !defined(OS_MACOSX)
-      windowless_buffer(NULL),
-      background_buffer(NULL)
+      windowless_buffer(TransportDIB::DefaultHandleValue()),
+      background_buffer(TransportDIB::DefaultHandleValue())
 #else
       ack_key(-1)
 #endif  // !defined(OS_MACOSX)
 {
 }
 
 PluginMsg_UpdateGeometry_Param::~PluginMsg_UpdateGeometry_Param() {
 }
 
 namespace IPC {
@@ skipping 233 matching lines @@
   l->append(", ");
   LogParam(p.transparent, l);
 #if defined(OS_MACOSX)
   l->append(", ");
   LogParam(p.ack_key, l);
 #endif
   l->append(")");
 }
 
 }  // namespace IPC