Fix broken context menu test in ActionHandler.

When running a user build with a phone target, proguard strips
openDocumentViewOnly which causes the test to fail.

Requiring the desktop handling flag means openDocumentViewOnly is
reachable by production code and therefore proguard won't strip it.

Bug: 393958917
Flag: EXEMPT Fixing a test
Test: Fixing a test

Change-Id: I45598949661e78ef3e474045637b0d1fe5ff683a