Fix nacl_helper argv bug, re-enable, build on linux except ARM

chrome/nacl/nacl_fork_delegate_linux.cc

 // Copyright (c) 2011 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/common/nacl_fork_delegate_linux.h"
 
 #include <signal.h>
 #include <stdlib.h>
 #include <sys/socket.h>
 
@@ skipping 28 matching lines @@
   // Confirm a couple hard-wired assumptions.
   // The NaCl constants are from chrome/nacl/nacl_linux_helper.h
   DCHECK(kNaClBrowserDescriptor == browserdesc);
   DCHECK(kNaClSandboxDescriptor == sandboxdesc);
 
   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], kNaClZygoteDescriptor));
   fds_to_map.push_back(std::make_pair(sandboxdesc, kNaClSandboxDescriptor));
   ready_ = false;
-  return;  // Disable nacl_helper while fixing some issues.
-
   FilePath helper_exe;
   FilePath helper_bootstrap_exe;
   if (PathService::Get(chrome::FILE_NACL_HELPER, &helper_exe) &&
       PathService::Get(chrome::FILE_NACL_HELPER_BOOTSTRAP,
                        &helper_bootstrap_exe) &&
       !RunningOnValgrind()) {
-    CommandLine::StringVector argv = CommandLine::ForCurrentProcess()->argv();
-    argv[0] = helper_bootstrap_exe.value();
-    argv[1] = helper_exe.value();
-    argv[2] = kNaClHelperAtZero;
+    CommandLine cmd_line(helper_bootstrap_exe);
+    cmd_line.AppendArgPath(helper_exe);
+    cmd_line.AppendArgNative(kNaClHelperAtZero);
     base::LaunchOptions options;
     options.fds_to_remap = &fds_to_map;
     options.clone_flags = CLONE_FS | SIGCHLD;
-    ready_ = base::LaunchProcess(argv, options, NULL);
+    ready_ = base::LaunchProcess(cmd_line.argv(), options, NULL);
     // parent and error cases are handled below
   }
   if (HANDLE_EINTR(close(fds[1])) != 0)
     LOG(ERROR) << "close(fds[1]) failed";
   if (ready_) {
     const ssize_t kExpectedLength = strlen(kNaClHelperStartupAck);
     char buf[kExpectedLength];
 
     // Wait for ack from nacl_helper, indicating it is ready to help
     const ssize_t nread = HANDLE_EINTR(read(fds[0], buf, sizeof(buf)));
@@ skipping 46 matching lines @@
 
 bool NaClForkDelegate::AckChild(const int fd,
                                 const std::string& channel_switch) {
   int nwritten = HANDLE_EINTR(write(fd, channel_switch.c_str(),
                                     channel_switch.length()));
   if (nwritten != static_cast<int>(channel_switch.length())) {
     return false;
   }
   return true;
 }