Upstream oodles of Chrome for Android code into Chromium.

Upstream oodles of Chrome for Android code into Chromium.

This adds plenty of Android-specific code (Java, C++, and resources) in a
few new folders:
 - chrome/android/java_staging: will be merged into chrome/android/java
   in the nearish future
 - chrome/android/javatests: chrome/android/javatests_shell will be merged into
   here incrementally as ChromeShell tests are converted to run against
   ChromePublic
 - chrome/test/android/javatests_staging: will be merged into
   chrome/test/android/javatests in the nearish future

There are two important new build targets: chrome_public_apk and
chrome_public_test_apk. chrome_public_apk is similar to chrome_shell_apk, but
with even more features.

Expected effect on bot times: The new tests take about 5 minutes to run.
Initially they'll be enabled on an FYI bot, but will soon be moved to the
CQ and main bots.

BUG=484934
R=cjhopman@chromium.org, jianli@chromium.org, maruel@chromium.org, mnaganov@chromium.org, sclittle@chromium.org, tedchoc@chromium.org, yfriedman@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/7497635a7cfdae2866d2aa7a3bd2894c895b8360