debugd: refactor out GetHelperPath from SandboxedProcess

This CL serves as a preemptive cleanup of SandboxedProcess.
$DEBUGD_HELPERS was also removed from debugd as it's not being
used anymore.

BUG=chromium:986272
TEST=emerge-${BOARD} debugd

Change-Id: Iac368d7ce495103f9305f942759732eb1142aa42
Reviewed-on: https://chromium-review.googlesource.com/1756399
Tested-by: Hardik Goyal <hardikgoyal@google.com>
Commit-Ready: Hardik Goyal <hardikgoyal@google.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Ben Chan <benchan@chromium.org>
diff --git a/debugd/src/process_with_output.cc b/debugd/src/process_with_output.cc
index 4ec0dad..66b9d77 100644
--- a/debugd/src/process_with_output.cc
+++ b/debugd/src/process_with_output.cc
@@ -11,6 +11,7 @@
 #include <base/strings/string_util.h>
 
 #include "debugd/src/error_utils.h"
+#include "debugd/src/helper_utils.h"
 
 namespace debugd {
 
@@ -118,7 +119,7 @@
                                  std::string* stderr,
                                  brillo::ErrorPtr* error) {
   std::string helper_path;
-  if (!SandboxedProcess::GetHelperPath(helper, &helper_path)) {
+  if (!GetHelperPath(helper, &helper_path)) {
     DEBUGD_ADD_ERROR(error, kDBusErrorString, kPathLengthErrorString);
     return kRunError;
   }