Include "invisible" volumes in new storage API.

The purpose of the new StorageVolume API is to grant access to
volumes that aren't typically "visible" to a developer, so include
them in the returned results.

Also return the real mounted state instead of augmenting based on
the caller's storage permissions.  Clean up API naming slightly and
return as List.

Bug: 27615770
Change-Id: Ida921a4b91e5af81e418e76f672d9108f45a9781
diff --git a/api/removed.txt b/api/removed.txt
index 36c8ce5..86085c8 100644
--- a/api/removed.txt
+++ b/api/removed.txt
@@ -136,6 +136,15 @@
 
 }
 
+package android.os.storage {
+
+  public class StorageManager {
+    method public android.os.storage.StorageVolume getPrimaryVolume();
+    method public android.os.storage.StorageVolume[] getVolumeList();
+  }
+
+}
+
 package android.preference {
 
   public class PreferenceManager {