Add a new devserver call to locate a file in build artifact

The new call `locate_file` looks up the given file name inside specified
build artifacts. One use case is to help caller to locate an apk file
inside a build artifact.

BUG=chromium:586320
TEST=local run devserver
curl
http://127.0.0.1:8082/locate_file?file_name=sl4a.apk\&target=shamu-userdebug\&build_id=2457013\&artifacts=test_zip\&branch=git_mnc-release\&os_type=android
expected retun: DATA/priv-app/sl4a/sl4a.apk
python devserver_integration_test.py

Change-Id: Ia029aae09b9bf52670c78fe2be4ccef62283ba41
Reviewed-on: https://chromium-review.googlesource.com/327278
Commit-Ready: Dan Shi <dshi@google.com>
Tested-by: Dan Shi <dshi@google.com>
Reviewed-by: Dan Shi <dshi@google.com>
3 files changed