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

ipc/ipc_tests.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 "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #elif defined(OS_POSIX)
 #include <sys/types.h>
@@ skipping 72 matching lines @@
   // kDebugChildren support.
   bool debug_on_start =
       CommandLine::ForCurrentProcess()->HasSwitch(switches::kDebugChildren);
 
   base::file_handle_mapping_vector fds_to_map;
   const int ipcfd = channel->GetClientFileDescriptor();
   if (ipcfd > -1) {
     fds_to_map.push_back(std::pair<int, int>(ipcfd, kPrimaryIPCChannel + 3));
   }
 
-  base::ProcessHandle ret = NULL;
+  base::ProcessHandle ret = base::kNullProcessHandle;
   switch (child_type) {
   case TEST_CLIENT:
     ret = MultiProcessTest::SpawnChild("RunTestClient",
                                        fds_to_map,
                                        debug_on_start);
     break;
   case TEST_DESCRIPTOR_CLIENT:
     ret = MultiProcessTest::SpawnChild("RunTestDescriptorClient",
                                        fds_to_map,
                                        debug_on_start);
@@ skipping 12 matching lines @@
     ret = MultiProcessTest::SpawnChild("RunFuzzServer",
                                        fds_to_map,
                                        debug_on_start);
     break;
   case SYNC_SOCKET_SERVER:
     ret = MultiProcessTest::SpawnChild("RunSyncSocketServer",
                                        fds_to_map,
                                        debug_on_start);
     break;
   default:
-    return NULL;
+    return base::kNullProcessHandle;
     break;
   }
   return ret;
 }
 #endif  // defined(OS_POSIX)
 
 TEST_F(IPCChannelTest, BasicMessageTest) {
   int v1 = 10;
   std::string v2("foobar");
   std::wstring v3(L"hello world");
@@ skipping 223 matching lines @@
 
   // setup IPC channel
   IPC::Channel chan(kTestClientChannel, IPC::Channel::MODE_CLIENT,
                     &channel_listener);
   CHECK(chan.Connect());
   channel_listener.Init(&chan);
   Send(&chan, "hello from child");
   // run message loop
   MessageLoop::current()->Run();
   // return true;
-  return NULL;
+  return 0;
 }
 
 #endif  // !PERFORMANCE_TEST
 
 #ifdef PERFORMANCE_TEST
 
 //-----------------------------------------------------------------------------
 // Manually performance test
 //
 //    This test times the roundtrip IPC message cycle. It is enabled with a
@@ skipping 156 matching lines @@
 #endif  // PERFORMANCE_TEST
 
 int main(int argc, char** argv) {
 #ifdef PERFORMANCE_TEST
   int retval = base::PerfTestSuite(argc, argv).Run();
 #else
   int retval = base::TestSuite(argc, argv).Run();
 #endif
   return retval;
 }