Update android generator to handle java7.

This is a combination of several commits made
to these files:

https://chromiumcodereview.appspot.com/23587011
https://codereview.chromium.org/23702057
https://codereview.chromium.org/40523002
https://codereview.chromium.org/49913003

Change-Id: Id944decfde8590c3a6e548ac66f598c45de7169e