Fix remoting_unittests that are failing on 32-bit linux

remoting/host/security_key/remote_security_key_ipc_constants.cc

 // Copyright 2016 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 "remoting/host/security_key/remote_security_key_ipc_constants.h"
 
+#include "base/environment.h"
 #include "base/lazy_instance.h"
 
 namespace {
 base::LazyInstance<std::string> g_remote_security_key_ipc_channel_name =
     LAZY_INSTANCE_INITIALIZER;
 
 const char kRemoteSecurityKeyIpcChannelName[] =
     "remote_security_key_ipc_channel";
 
 }  // namespace
@@ skipping 10 matching lines @@
   }
 
   return g_remote_security_key_ipc_channel_name.Get();
 }
 
 void SetRemoteSecurityKeyIpcChannelNameForTest(
     const std::string& channel_name) {
   g_remote_security_key_ipc_channel_name.Get() = channel_name;
 }
 
+std::string GetChannelNamePathPrefixForTest() {
+  std::string path_prefix;
+#if defined(OS_LINUX)
+  path_prefix = "/dev/socket/";
+  std::unique_ptr<base::Environment> env(base::Environment::Create());
+  if (env->GetVar(base::env_vars::kHome, &path_prefix))
+    path_prefix += "/";
+#endif
+  return path_prefix;
+}
+
 }  // namespace remoting