Gallery2: Use ICS alert drawable

Same bug here. It's using the old compability drawable
instead of the Holo theme one.

Change-Id: Ia84ce1d305ee63fc6bc1fdb407a91b3421842eb1
diff --git a/src/com/android/gallery3d/app/AbstractGalleryActivity.java b/src/com/android/gallery3d/app/AbstractGalleryActivity.java
index d25f60e..9500fff 100644
--- a/src/com/android/gallery3d/app/AbstractGalleryActivity.java
+++ b/src/com/android/gallery3d/app/AbstractGalleryActivity.java
@@ -142,7 +142,7 @@
                 }
             };
             mAlertDialog = new AlertDialog.Builder(this)
-                    .setIcon(android.R.drawable.ic_dialog_alert)
+                    .setIconAttribute(android.R.attr.alertDialogIcon)
                     .setTitle("No Storage")
                     .setMessage("No external storage available.")
                     .setNegativeButton(android.R.string.cancel, onClick)