Add the ability to change directories before execing.

base/process/launch_posix.cc

Index: base/process/launch_posix.cc
diff --git a/base/process/launch_posix.cc b/base/process/launch_posix.cc
index ce93d5056fd838bf332da563186c5bc704130e22..203b7c8b9a71830f3a21e72e6700695dbdc76aef 100644
--- a/base/process/launch_posix.cc
+++ b/base/process/launch_posix.cc
@@ -347,7 +347,12 @@ Process LaunchProcess(const std::vector<std::string>& argv,
   fd_shuffle1.reserve(fd_shuffle_size);
   fd_shuffle2.reserve(fd_shuffle_size);
 
-  scoped_ptr<char*[]> argv_cstr(new char*[argv.size() + 1]);
+  scoped_ptr<char* []> argv_cstr(new char* [argv.size() + 1]);
+  for (size_t i = 0; i < argv.size(); i++) {
+    argv_cstr[i] = const_cast<char*>(argv[i].c_str());
+  }
+  argv_cstr[argv.size()] = NULL;
+
   scoped_ptr<char*[]> new_environ;
   char* const empty_environ = NULL;
   char* const* old_environ = GetEnvironment();
@@ -360,6 +365,11 @@ Process LaunchProcess(const std::vector<std::string>& argv,
   sigfillset(&full_sigset);
   const sigset_t orig_sigmask = SetSignalMask(full_sigset);
 
+  const char* current_directory = nullptr;
+  if (!options.current_directory.empty()) {
+    current_directory = options.current_directory.value().c_str();
+  }
+
   pid_t pid;
 #if defined(OS_LINUX)
   if (options.clone_flags) {
@@ -515,15 +525,14 @@ Process LaunchProcess(const std::vector<std::string>& argv,
     }
 #endif
 
-#if defined(OS_POSIX)
+    if (current_directory != nullptr) {
+      RAW_CHECK(chdir(current_directory) == 0);
+    }
+
     if (options.pre_exec_delegate != nullptr) {
       options.pre_exec_delegate->RunAsyncSafe();
     }
-#endif
 
-    for (size_t i = 0; i < argv.size(); i++)
-      argv_cstr[i] = const_cast<char*>(argv[i].c_str());
-    argv_cstr[argv.size()] = NULL;
     execvp(argv_cstr[0], argv_cstr.get());
 
     RAW_LOG(ERROR, "LaunchProcess: failed to execvp:");