Revert of Make generate_gradle.py work with preview SDKs. (patchset #1 id:1 of https://codereview.chromium.org/2724513003/ )

Reason for revert:
Breaks when CWD != output_dir

Original issue's description:
> Make generate_gradle.py work with preview SDKs.
>
> This just tweaks the values of buildToolsVersion and compileSdkVersion,
> which were not being set in a way compatible with preview SDKs.
>
> BUG=620034
>
> Review-Url: https://codereview.chromium.org/2724513003
> Cr-Commit-Position: refs/heads/master@{#453737}
> Committed: https://chromium.googlesource.com/chromium/src/+/1a04e1cf3d4912300d625a57318bc6f2ba53ba79

TBR=estevenson@chromium.org,nyquist@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=620034

Review-Url: https://codereview.chromium.org/2722973002
Cr-Commit-Position: refs/heads/master@{#453788}
2 files changed