Handle volumes without visible paths.

Transient volumes like USB drives are not mounted as visible, so we
shouldn't be kicking off media scanner for them.

Bug: 22545248
Change-Id: Ic8f2d3134f1edb8b2a12e8ff283eceeeb230f48b

Author: jsharkey

packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java

@@ -162,7 +162,11 @@ private void updateVolumesLocked() {
                 if (volume.getType() == VolumeInfo.TYPE_PUBLIC) {
                     root.flags |= Root.FLAG_HAS_SETTINGS;
                 }
-                root.visiblePath = volume.getPathForUser(userId);
+                if (volume.isVisibleForRead(userId)) {
+                    root.visiblePath = volume.getPathForUser(userId);
+                } else {
+                    root.visiblePath = null;
+                }
                 root.path = volume.getInternalPathForUser(userId);
                 root.docId = getDocIdForFile(root.path);