Let breakpad build with -Wall on OS X and Linux.

src/common/dwarf/dwarf2reader.h

 // -*- mode: C++ -*-
 
 // Copyright (c) 2010 Google Inc. 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.
@@ skipping 122 matching lines @@
   // A DWARF2/3 line info header.  This is not the same size as
   // in the actual file, as the one in the file may have a 32 bit or
   // 64 bit lengths
 
   struct LineInfoHeader header_;
 
   // buffer is the buffer for our line info, starting at exactly where
   // the line info to read is.  after_header is the place right after
   // the end of the line information header.
   const char* buffer_;
+#ifndef NDEBUG
   uint64 buffer_length_;
+#endif
   const char* after_header_;
 };
 
 // This class is the main interface between the line info reader and
 // the client.  The virtual functions inside this get called for
 // interesting events that happen during line info reading.  The
 // default implementation does nothing
 
 class LineInfoHandler {
  public:
@@ skipping 887 matching lines @@
   // The name of the file whose CFI we're reading.
   string filename_;
 
   // The name of the CFI section in that file.
   string section_;
 };
 
 }  // namespace dwarf2reader
 
 #endif  // UTIL_DEBUGINFO_DWARF2READER_H__