Fix compatibility with Robolectric.

Robolectric at somepoint changed to return a valid Java ClassLoader from
Context.getClassLoader(), breaking the check in MultiDex.

Modify this check to ensure a valid Dex compatible classloader.

Test: Added integration tests in Robolectric; m -j checkbuild
Change-Id: I9df517e25460daa5fabfe8cba88cdc5d9bb16de2
3 files changed