Android: Remove build/secondary

Move the build targets to //third_party/android_sdk.
Move files for android_platform into //third_party/android_platform.

Tbr for build target renaming.

Tbr: thakis@chromium.org
Bug: 947060
Change-Id: I1ec7117b042a2bfe22c6dbc7985256465318cab7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1543468


Commit-Queue: Peter Wen <wnwen@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#645538}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 22bc3ec1ab45842fc3fa00ad2b1924680b678118