PrependWrapper is platform-specific, so it should take a platform string.

chrome/browser/zygote_host_linux.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/zygote_host_linux.h"
 
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
@@ skipping 63 matching lines @@
 
   cmd_line.AppendSwitchASCII(switches::kProcessType, switches::kZygoteProcess);
 
   int fds[2];
   CHECK(socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fds) == 0);
   base::file_handle_mapping_vector fds_to_map;
   fds_to_map.push_back(std::make_pair(fds[1], 3));
 
   const CommandLine& browser_command_line = *CommandLine::ForCurrentProcess();
   if (browser_command_line.HasSwitch(switches::kZygoteCmdPrefix)) {
-    const std::wstring prefix =
-        browser_command_line.GetSwitchValue(switches::kZygoteCmdPrefix);
-    cmd_line.PrependWrapper(prefix);
+    cmd_line.PrependWrapper(
+        browser_command_line.GetSwitchValueNative(switches::kZygoteCmdPrefix));
   }
   // Append any switches from the browser process that need to be forwarded on
   // to the zygote/renderers.
   // Should this list be obtained from browser_render_process_host.cc?
   static const char* kForwardSwitches[] = {
     switches::kAllowSandboxDebugging,
     switches::kLoggingLevel,
     switches::kEnableLogging,  // Support, e.g., --enable-logging=stderr.
     switches::kUserDataDir,  // Make logs go to the right file.
     // Load (in-process) Pepper plugins in-process in the zygote pre-sandbox.
     switches::kRegisterPepperPlugins,
 #if defined(USE_SECCOMP_SANDBOX)
     switches::kDisableSeccompSandbox,
 #else
     switches::kEnableSeccompSandbox,
 #endif
   };
   cmd_line.CopySwitchesFrom(browser_command_line, kForwardSwitches,
                             arraysize(kForwardSwitches));
 
   sandbox_binary_ = sandbox_cmd.c_str();
   struct stat st;
 
   if (!sandbox_cmd.empty() && stat(sandbox_binary_.c_str(), &st) == 0) {
     if (access(sandbox_binary_.c_str(), X_OK) == 0 &&
         (st.st_uid == 0) &&
         (st.st_mode & S_ISUID) &&
         (st.st_mode & S_IXOTH)) {
       using_suid_sandbox_ = true;
-      cmd_line.PrependWrapper(ASCIIToWide(sandbox_binary_.c_str()));
+      cmd_line.PrependWrapper(sandbox_binary_);
 
       SaveSUIDUnsafeEnvironmentVariables();
     } else {
       LOG(FATAL) << "The SUID sandbox helper binary was found, but is not "
                     "configured correctly. Rather than run without sandboxing "
                     "I'm aborting now. You need to make sure that "
                  << sandbox_binary_ << " is mode 4755 and owned by root.";
     }
   }
 
@@ skipping 209 matching lines @@
       !read_pickle.ReadBool(&iter, &tmp_child_exited)) {
     LOG(WARNING) << "Error parsing DidProcessCrash response from zygote.";
     return false;
   }
 
   if (child_exited)
     *child_exited = tmp_child_exited;
 
   return did_crash;
 }