[ChromeDriver] W3c-compliant proxyType parsing

The proxyType string should be handled case-sensitively in W3C mode.
Resolves 2 WPT test failures in
webdriver/tests/new_session/invalid_capabilities.py.

Bug: chromedriver:1997
Change-Id: If931b4d1d982aae8646e9b5783cbf7ee52fa4b60
Reviewed-on: https://chromium-review.googlesource.com/c/1355437
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612369}
2 files changed