Fix temporary directory path in Android.

We should use /data/misc/update_engine/tmp instead of /data/local/tmp.

Bug: 24478450
TEST=Delta update nolonger permission denied.

Change-Id: I9a8096e602320195d30147971def5145bd82d775
diff --git a/common/hardware_chromeos.cc b/common/hardware_chromeos.cc
index ae27e36..f93685d 100644
--- a/common/hardware_chromeos.cc
+++ b/common/hardware_chromeos.cc
@@ -29,6 +29,7 @@
 
 #include "update_engine/common/hardware.h"
 #include "update_engine/common/hwid_override.h"
+#include "update_engine/common/platform_constants.h"
 #include "update_engine/common/subprocess.h"
 #include "update_engine/common/utils.h"
 
@@ -49,10 +50,6 @@
 // a powerwash is performed.
 const char kPowerwashCountMarker[] = "powerwash_count";
 
-// The stateful directory used by update_engine. This directory is wiped during
-// powerwash.
-const char kNonVolatileDirectory[] = "/var/lib/update_engine";
-
 }  // namespace
 
 namespace chromeos_update_engine {
@@ -144,7 +141,7 @@
 }
 
 bool HardwareChromeOS::GetNonVolatileDirectory(base::FilePath* path) const {
-  *path = base::FilePath(kNonVolatileDirectory);
+  *path = base::FilePath(constants::kNonVolatileDirectory);
   return true;
 }