arcvm: Pass Chrome OS user id hash to arcvm-mount-myfiles upstart job

We are going to mount /home/.shadow/<user-hash>/mount/user/MyFiles
instead of /home/chronos/user/MyFiles in the arcvm-mount-myfiles upstart
job. In order to achieve it, this CL makes ArcVmClientAdapter pass the
Chrome OS user id hash to the upstart job.

BUG=b:123641356
TEST=$ components_unittests --gtest_filter="ArcVmClientAdapterTest.*"
TEST=Confirm that ${CHROMEOS_USER_ID_HASH} is available in the
TEST=arcvm-mount-myfiles upstart job.

Change-Id: I4adac56aadd7cf4f5f513921b1ccc7c8f874f077
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2412112Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Reviewed-by: Satoshi Niwa <niwa@chromium.org>
Commit-Queue: Youkichi Hosoi <youkichihosoi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807854}

components/arc/session/arc_vm_client_adapter.cc

@@ -700,11 +700,14 @@ class ArcVmClientAdapter : public ArcClientAdapter,
         "CHROMEOS_USER=" +
         cryptohome::CreateAccountIdentifierFromIdentification(cryptohome_id_)
             .account_id()};
+    std::vector<std::string> environment_for_arcvm_mount_myfiles = {
+        "CHROMEOS_USER_ID_HASH=" + user_id_hash_};
     std::deque<JobDesc> jobs{
         JobDesc{kArcVmServerProxyJobName, UpstartOperation::JOB_START, {}},
         JobDesc{kArcCreateDataJobName, UpstartOperation::JOB_START,
                 std::move(environment_for_create_data)},
-        JobDesc{kArcVmMountMyFilesJobName, UpstartOperation::JOB_START, {}},
+        JobDesc{kArcVmMountMyFilesJobName, UpstartOperation::JOB_START,
+                std::move(environment_for_arcvm_mount_myfiles)},
         JobDesc{
             kArcVmMountRemovableMediaJobName, UpstartOperation::JOB_START, {}},
     };