WebDriver: Add support to import and run W3C tests

WebDriver: Add support to import and run W3C tests
https://bugs.webkit.org/show_bug.cgi?id=177304

Reviewed by Brian Burg.

Tools:

WPT has now several WebDriver tests, and new ones are going to be added to cover the whole spec. This patch
adds the initial support for running W3C tests. The script import-w3c-webdriver-tests reuses parts of the W3C
test downloader to download the tests and required tools from WPT repository into WebDriverTests
directory. Tests can be run with run-webdriver-tests, a new script that works similar to other test runner
scripts. For now it shows a summary at the end of the execution, there aren't expectations yet, since we are not
ready to run those tests in the bots. Once we are ready to properly run the tests, we can add the expectations
support and run the tests in the bots.

* Scripts/import-w3c-webdriver-tests: Added.
* Scripts/run-webdriver-tests: Added.
* Scripts/webkitpy/style/checker.py: Skip WebDriverTests directory since it only contains third-party python
code.
* Scripts/webkitpy/thirdparty/__init__.py: Add support to autodownload mozlog and mozprocess since they are
required by the WebDriver tests.
* Scripts/webkitpy/webdriver_tests/__init__.py: Added.
* Scripts/webkitpy/webdriver_tests/webdriver_driver.py: Added.
* Scripts/webkitpy/webdriver_tests/webdriver_driver_gtk.py: Added.
* Scripts/webkitpy/webdriver_tests/webdriver_test_result.py: Added.
* Scripts/webkitpy/webdriver_tests/webdriver_test_runner.py: Added.
* Scripts/webkitpy/webdriver_tests/webdriver_test_runner_w3c.py: Added.
* Scripts/webkitpy/webdriver_tests/webdriver_w3c_executor.py: Added.
* Scripts/webkitpy/webdriver_tests/webdriver_w3c_web_server.py: Added.

WebDriverTests:

Add json file used by the importer and the result of running the importer.

* imported/w3c/importer.json: Added.
* imported/w3c/tools/pytest/: Added.
* imported/w3c/tools/webdriver/: Added.
* imported/w3c/tools/wptrunner/: Added.
* imported/w3c/webdriver/: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@224014 268f45cc-cd09-0410-ab3c-d52691b4dbfc