Builder failure: https://ci.chromium.org/buildbot/chromium/Android/79291
It's super flaky but it did happen.

Failure reason:
[37782/73564] ACTION //chrome/test/chromedriver/test/webview_shell:chromedriver_webview_shell_apk__create__package_apk(//build/toolchain/android:android_clang_arm)
FAILED: gen/chrome/test/chromedriver/test/webview_shell/chromedriver_webview_shell_apk/chromedriver_webview_shell_apk_unsigned.apk 
python ../../build/android/gyp/apkbuilder.py --depfile gen/chrome/test/chromedriver/test/webview_shell/chromedriver_webview_shell_apk__create__package_apk.d --resource-apk=gen/arsc/apks/ChromeDriverWebViewShell.ap_ --output-apk=gen/chrome/test/chromedriver/test/webview_shell/chromedriver_webview_shell_apk/chromedriver_webview_shell_apk_unsigned.apk --assets=@FileArg\(gen/chrome/test/chromedriver/test/webview_shell/chromedriver_webview_shell_apk.build_config:assets\) --uncompressed-assets=@FileArg\(gen/chrome/test/chromedriver/test/webview_shell/chromedriver_webview_shell_apk.build_config:uncompressed_assets\) --java-resources=@FileArg\(gen/chrome/test/chromedriver/test/webview_shell/chromedriver_webview_shell_apk.build_config:java_resources_jars\) --apk-pak-info-path size-info/ChromeDriverWebViewShell.apk.pak.info --dex-file=gen/chrome/test/chromedriver/test/webview_shell/chromedriver_webview_shell_apk/classes.dex
Traceback (most recent call last):
  File "../../build/android/gyp/apkbuilder.py", line 346, in <module>
    main(sys.argv[1:])
  File "../../build/android/gyp/apkbuilder.py", line 342, in main
    depfile_deps=depfile_deps)
  File "/b/c/b/Android/src/build/android/gyp/util/build_utils.py", line 602, in CallAndWriteDepfileIfStale
    pass_changes=True)
  File "/b/c/b/Android/src/build/android/gyp/util/md5_check.py", line 87, in CallAndRecordIfStale
    function(*args)
  File "/b/c/b/Android/src/build/android/gyp/util/build_utils.py", line 585, in on_stale_md5
    function(*args)
  File "../../build/android/gyp/apkbuilder.py", line 329, in on_stale_md5
    options.assets + options.uncompressed_assets)
  File "../../build/android/gyp/apkbuilder.py", line 199, in _MergePakInfoFiles
    os.makedirs(info_dir)
  File "/usr/lib/python2.7/os.py", line 157, in makedirs
    mkdir(name, mode)
OSError: [Errno 17] File exists: 'size-info'

Even though we check that path doesn't exists before create a directory, it seems that someone else can create the same directory in parallel.

  # Ensure that parent dirs exist before writing new files.
  info_dir = os.path.dirname(pak_info_path)
  if not os.path.exists(info_dir):
    os.makedirs(info_dir)

Adding a try-catch block may help