Clean up stale java in explicit bindings generator gypi

Clean up stale java in explicit bindings generator gypi

This applies the same approach as r318190 to clean up
stale generated java when any mojom dependencies have
changed in gyp targets using
mojom_bindings_generator_explicit.gypi.

BUG=461622
R=jamesr@chromium.org

Committed: https://crrev.com/7a8e7054cd6d3a8ce9a5891f021629de94d8ae86
Cr-Commit-Position: refs/heads/master@{#318554}

[Ken Rockot(use gerrit already), 2015-02-27 17:16:36]

rockot@chromium.org changed reviewers:
+ cjhopman@chromium.org

[Ken Rockot(use gerrit already), 2015-02-27 17:16:36]

+cjhopman for sanity check. This is similar to the other recent CL, just another
source of mojom-generated java bindings that can go stale. These are also
blocking the mojo roll

[cjhopman, 2015-02-27 23:03:55]

lgtm

[jamesr, 2015-02-27 23:04:19]

lgtm

[Ken Rockot(use gerrit already), 2015-02-27 23:05:48]

The CQ bit was checked by rockot@chromium.org

[commit-bot: I haz the power, 2015-02-27 23:07:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/963773002/1

[commit-bot: I haz the power, 2015-02-28 00:06:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-28 00:06:55]

Patchset 1 (id:??) landed as
https://crrev.com/7a8e7054cd6d3a8ce9a5891f021629de94d8ae86
Cr-Commit-Position: refs/heads/master@{#318554}