Add an optional root prefix to Linux dumpers

src/client/linux/minidump_writer/linux_core_dumper.h

 // Copyright (c) 2012, 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.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 29 matching lines @@
 
 namespace google_breakpad {
 
 class LinuxCoreDumper : public LinuxDumper {
  public:
   // Constructs a dumper for extracting information of a given process
   // with a process ID of |pid| via its core dump file at |core_path| and
   // its proc files at |procfs_path|. If |procfs_path| is a copy of
   // /proc/<pid>, it should contain the following files:
   //     auxv, cmdline, environ, exe, maps, status
-  LinuxCoreDumper(pid_t pid, const char* core_path, const char* procfs_path);
+  // See LinuxDumper for the purpose of |root_prefix|.
+  LinuxCoreDumper(pid_t pid, const char* core_path, const char* procfs_path,
+                  const char* root_prefix = "");
 
   // Implements LinuxDumper::BuildProcPath().
   // Builds a proc path for a certain pid for a node (/proc/<pid>/<node>).
   // |path| is a character array of at least NAME_MAX bytes to return the
   // result.|node| is the final node without any slashes. Return true on
   // success.
   //
   // As this dumper performs a post-mortem dump and makes use of a copy
   // of the proc files of the crashed process, this derived method does
   // not actually make use of |pid| and always returns a subpath of
@@ skipping 53 matching lines @@
   // Content of the core dump file.
   ElfCoreDump core_;
 
   // Thread info found in the core dump file.
   wasteful_vector<ThreadInfo> thread_infos_;
 };
 
 }  // namespace google_breakpad
 
 #endif  // CLIENT_LINUX_HANDLER_LINUX_CORE_DUMPER_H_