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

chrome/browser/sync/syncable/syncable.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 "chrome/browser/sync/syncable/syncable.h"
 
 #include "build/build_config.h"
 
 #include <sys/stat.h>
 #if defined(OS_POSIX)
@@ skipping 1069 matching lines @@
   : directory_(directory), dirkernel_(directory->kernel_), name_(name),
     source_file_(source_file), line_(line), writer_(writer) {
   Lock();
 }
 
 BaseTransaction::BaseTransaction(Directory* directory)
     : directory_(directory),
       dirkernel_(NULL),
       name_(NULL),
       source_file_(NULL),
-      line_(NULL),
+      line_(0),
       writer_(INVALID) {
 }
 
 BaseTransaction::~BaseTransaction() {}
 
 void BaseTransaction::UnlockAndLog(OriginalEntries* originals_arg) {
   // Triggers the CALCULATE_CHANGES and TRANSACTION_ENDING events while
   // holding dir_kernel_'s transaction_mutex and changes_channel mutex.
   // Releases all mutexes upon completion.
   if (!NotifyTransactionChangingAndEnding(originals_arg)) {
@@ skipping 629 matching lines @@
 
 FastDump& operator<<(FastDump& dump, const Blob& blob) {
   if (blob.empty())
     return dump;
   string buffer(base::HexEncode(&blob[0], blob.size()));
   dump.out_->sputn(buffer.c_str(), buffer.size());
   return dump;
 }
 
 }  // namespace syncable