Removing third_party/android_async_task

Bug: 825947
Change-Id: Id03b7c06a7173afb7b15e64eb91974735a979c0d
Reviewed-on: https://chromium-review.googlesource.com/1240514Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Sam Maier <smaier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593597}

third_party/android_async_task/OWNERS

-agrieve@chromium.org
-hartmanng@chromium.org
-smaier@chromium.org
-torne@chromium.org
-wnwen@chromium.org

third_party/android_async_task/README.chromium

-Name: AsyncTask
-URL: https://android.googlesource.com/platform/frameworks/base/+/oreo-release/core/java/android/os/AsyncTask.java
-Version: 1488a3a19d4681a41fb45570c15e14d99db1cb66
-License: Apache 2.0
-License File: LICENSE
-Security Critical: yes
-
-Description:
-This contains a copy of Android Oreo's AsyncTask.java.
-
-Local Modifications:
-- Renamed package to org.chromium.base.
-- Explicitly import android.os objects.
-- Switch to using android.support.annotations (from android.support.v13).
-- Added annotations to help it compile issue-free.
-- Changed THREAD_POOL_EXECUTOR to use our extension of Android's
-  ThreadPoolExecutor (which adds information about the work queue when it fills
-  up)
-- Added function which shuts down Android's ThreadPoolExecutor, and rerouted
-  runnables sent to Android's ThreadPoolExecutor to our Executor.
-- Changed SERIAL_EXECUTOR to reuse the executor from android.os.AsyncTask
-- Removed Params, Progress generics