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* Use dist_jar() rather than a custom script
  * Avoids needing to extract .jars.
  * Avoids needing to reference ".javac.jar" files, which
    are somewhat of an implementation detail.

* Added jar_excluded_patterns support to dist_jar()

* Merges zip.py and dist_jar.py, since they were doing the
  same thing.

Spot checked that these two jars are the same before/after:
* cronet/cronet_impl_common_java.jar
* cronet/cronet_impl_native_java.jar

Change-Id: I4d5a5f495ce0376ef2e53b6d4e3c9ebbc3d75ae1
Reviewed-on: https://chromium-review.googlesource.com/c/1349872Reviewed-by: Paul Jensen <pauljensen@chromium.org>
Reviewed-by: Eric Stevenson <estevenson@chromium.org>
Commit-Queue: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612210}