Set MyFiles as visible device

In the Android CLs, we allow this to happen and we prohibited the
creation of the Android directories. So apps can access the MyFiles
through Storage frameworks, but no default directories to be
created.

BUG=b:162793388
BUG=b:169537013
TEST=Manual test in Photos app, CtsAppSecurityHostTestCases,
CtsProviderTestCases, part of CtsMediaTestCases

Change-Id: I98ab33d6d68adfb1638bcdf07557817df257c6f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2536424Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Reviewed-by: Naoki Fukino <fukino@chromium.org>
Commit-Queue: Risan <risan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#830496}

components/arc/volume_mounter/arc_volume_mounter_bridge.cc

@@ -16,6 +16,7 @@
 #include "components/arc/arc_browser_context_keyed_service_factory_base.h"
 #include "components/arc/arc_features.h"
 #include "components/arc/arc_prefs.h"
+#include "components/arc/arc_util.h"
 #include "components/arc/session/arc_bridge_service.h"
 #include "components/prefs/pref_service.h"
 #include "components/user_prefs/user_prefs.h"
@@ -131,9 +132,11 @@ void ArcVolumeMounterBridge::SendMountEventForMyFiles() {
   // TODO(niwa): Add a new DeviceType enum value for MyFiles.
   chromeos::DeviceType device_type = chromeos::DeviceType::DEVICE_TYPE_SD;
 
+  // Conditionally set MyFiles to be visible for P and invisible for R. In R, we use IsVisibleRead
+  // so this is not needed.
   volume_mounter_instance->OnMountEvent(mojom::MountPointInfo::New(
       DiskMountManager::MOUNTING, kMyFilesPath, kMyFilesPath, kMyFilesUuid,
-      device_label, device_type, false));
+      device_label, device_type, !IsArcVmEnabled()));
 }
 
 bool ArcVolumeMounterBridge::IsVisibleToAndroidApps(