[DO NOT MERGE] Explicitly keep relevant LogBuffer classes for plugins am:...

[DO NOT MERGE] Explicitly keep relevant LogBuffer classes for plugins am: 084a2c24 am: 2fd40560 am: 48b7d6eb

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23417280



Change-Id: Ib57fd4f40854dfba3cc7f9c1adc9e3335d1cb2ae
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>