Add buildExternalStorageAndroidObbDirs().

For use by DownloadManager.

Bug: 153504419
Test: atest CtsDownloadManagerInstaller
Change-Id: Ifd45ad779087fb5ba3d885d8e648bc24bc8656eb
diff --git a/core/java/android/os/Environment.java b/core/java/android/os/Environment.java
index 5f8c4f5..eaadabd 100644
--- a/core/java/android/os/Environment.java
+++ b/core/java/android/os/Environment.java
@@ -971,6 +971,15 @@
     }
 
     /**
+     * Returns the path for android-specific OBB data on the SD card.
+     * @hide
+     */
+    public static File[] buildExternalStorageAndroidObbDirs() {
+        throwIfUserRequired();
+        return sCurrentUser.buildExternalStorageAndroidObbDirs();
+    }
+
+    /**
      * Generates the raw path to an application's data
      * @hide
      */