update_engine: use shared DLC path strings

Use shared path strings for DLC install path.

BUG=chromium:923592
TEST=emerge-kefka update_engine
CQ-DEPEND=CL:1436377

Change-Id: Ica9ba9ae3432cb3fafdb4be54413fb61c2477c88
Reviewed-on: https://chromium-review.googlesource.com/1436118
Commit-Ready: Xiaochu Liu <xiaochu@chromium.org>
Tested-by: Xiaochu Liu <xiaochu@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/boot_control_chromeos.cc b/boot_control_chromeos.cc
index ccba316..b390f61 100644
--- a/boot_control_chromeos.cc
+++ b/boot_control_chromeos.cc
@@ -24,6 +24,7 @@
 #include <base/files/file_path.h>
 #include <base/files/file_util.h>
 #include <base/strings/string_util.h>
+#include <chromeos/constants/imageloader.h>
 #include <rootdev/rootdev.h>
 
 extern "C" {
@@ -43,7 +44,6 @@
 const char* kAndroidPartitionNameKernel = "boot";
 const char* kAndroidPartitionNameRoot = "system";
 
-const char kDlcInstallRootDirectoryEncrypted[] = "/home/chronos/dlc";
 const char kPartitionNamePrefixDlc[] = "dlc_";
 const char kPartitionNameDlcA[] = "dlc_a";
 const char kPartitionNameDlcB[] = "dlc_b";
@@ -161,7 +161,7 @@
                  << partition_name;
       return false;
     }
-    *device = base::FilePath(kDlcInstallRootDirectoryEncrypted)
+    *device = base::FilePath(imageloader::kDlcImageRootpath)
                   .Append(dlc_module_id)
                   .Append(slot == 0 ? kPartitionNameDlcA : kPartitionNameDlcB)
                   .Append(kPartitionNameDlcImage)