Per-app media directories on external storage.

This change defines per-app directories on external storage that
will be scanned and included in MediaStore.  This gives apps a way
to write content to secondary shared storage in a way that can
easily be surfaced to other apps.

Bug: 14382377
Change-Id: I4cb367c870509e76f0c2c598f01e2f699780030a
diff --git a/core/java/android/os/Environment.java b/core/java/android/os/Environment.java
index e98a26b..e84b695 100644
--- a/core/java/android/os/Environment.java
+++ b/core/java/android/os/Environment.java
@@ -191,6 +191,10 @@
             return buildPaths(mExternalDirsForApp, DIR_ANDROID, DIR_MEDIA, packageName);
         }
 
+        public File[] buildExternalStorageAppMediaDirsForVold(String packageName) {
+            return buildPaths(mExternalDirsForVold, DIR_ANDROID, DIR_MEDIA, packageName);
+        }
+
         public File[] buildExternalStorageAppObbDirs(String packageName) {
             return buildPaths(mExternalDirsForApp, DIR_ANDROID, DIR_OBB, packageName);
         }