Cronet team is working around this by distributing the .javac.jar files:

https://cs.chromium.org/chromium/src/components/cronet/android/BUILD.gn?q=cronet+javac.jar&sq=package:chromium&l=1243

We could move the template into the common rules if that's something you'd like to use as well.

Nice to hear we are not the only ones with this issue. Ideally, I think
this should be a flag to dist_jar template. I can experiment with the
template to see if it works for us.

Adding it to dist_jar sgtm.

The following revision refers to this bug:
  https://webrtc.googlesource.com/src.git/+/7bc55b8e84e76c60d55e33c017858d9cb0984225

commit 7bc55b8e84e76c60d55e33c017858d9cb0984225
Author: Sami Kalliomäki <sakal@webrtc.org>
Date: Thu Nov 23 13:25:58 2017

Update AAR-generation to use non-preprocessed jar files.

Previously Java 8 bytecode was transpiled into Java 7 bytecode for AAR.
With this change we instead include Java 8 bytecode in the AAR.

This drops support for Java 7 but allows using Java 8 features such as
static methods in interfaces and default methods.

Bug:  webrtc:8084 ,  chromium:762967 
Change-Id: I3c6ec9332c5612b7ed811a81957f25c94c80da70
No-Try: True
Reviewed-on: https://webrtc-review.googlesource.com/21222
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20849}
[modify] https://crrev.com/7bc55b8e84e76c60d55e33c017858d9cb0984225/sdk/android/BUILD.gn

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/648e9a6566e497a173b1a0b2fbf76c0e829163da

commit 648e9a6566e497a173b1a0b2fbf76c0e829163da
Author: Andrew Grieve <agrieve@chromium.org>
Date: Fri Dec 22 20:45:28 2017

Adds an android_aar() target, which can create Android Libraries.

See: https://developer.android.com/studio/projects/android-library.html

webrtc and cronet have both expressed interest in this at one point or
another. While this doesn't support all aar features, it's a good start
(and wasn't that hard).

Bug:  506230 ,  762967 
Change-Id: I1a5144311c1e7a30ccd2a50f77183977d820ea78
Reviewed-on: https://chromium-review.googlesource.com/841862
Commit-Queue: agrieve <agrieve@chromium.org>
Reviewed-by: Eric Stevenson <estevenson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526055}
[add] https://crrev.com/648e9a6566e497a173b1a0b2fbf76c0e829163da/build/android/gyp/dist_aar.py
[modify] https://crrev.com/648e9a6566e497a173b1a0b2fbf76c0e829163da/build/android/gyp/write_build_config.py
[modify] https://crrev.com/648e9a6566e497a173b1a0b2fbf76c0e829163da/build/config/android/internal_rules.gni
[modify] https://crrev.com/648e9a6566e497a173b1a0b2fbf76c0e829163da/build/config/android/rules.gni