[Linux] run-benchmark should be able to execute the benchmarks with more browsers.

[Linux] run-benchmark should be able to execute the benchmarks with more browsers.
https://bugs.webkit.org/show_bug.cgi?id=164792

Reviewed by Michael Catanzaro.

This removes the GTKBrowserDriver (and the platform 'gtk') from the run-benchmark script,
and adds a new LinuxBrowserDriver with a platform 'linux'.

It add also drivers for Chrome (Chromium), Firefox, Epiphany and MiniBrowser-GTK (previously MiniBrowser).

The detection of the platform is now done automatically, so it is not longer needed to pass a "--platform" parameter.

The tracking of the browser process is now more robust, we track the pid of the browser process and we only try to
kill the ones that were executed by this script, instead of doing a 'killall $browser' (like before).
We also check for browser process childs and we kill them if they are still alive after the main browser process has been killed.
This depends on psutil, so this will only be done if psutil is installed.

* BuildSlaveSupport/build.webkit.org-config/master.cfg:
(RunBenchmarkTests.start): The platform is now autodetected and the MiniBrowser driver is renamed to MiniBrowser-GTK.
* Scripts/webkitpy/benchmark_runner/benchmark_runner.py:
(BenchmarkRunner._run_benchmark): Fix a bug that caused close_browsers to be called twice. Its already called inside BenchmarkRunner._run_one_test.
* Scripts/webkitpy/benchmark_runner/browser_driver/linux_browser_driver.py: Added.
(LinuxBrowserDriver): Implement base class that has all the needed functionality for driving the browsers.
(LinuxBrowserDriver.__init__):
(LinuxBrowserDriver.prepare_env):
(LinuxBrowserDriver.restore_env):
(LinuxBrowserDriver.close_browsers): Made the dependency on psutil optional (because it was listed as such on the README file <Tools/Scripts/webkitpy/benchmark_runner/README.md>)
(LinuxBrowserDriver.launch_url):
(LinuxBrowserDriver._get_first_executable_path_from_list):
(LinuxBrowserDriver._screen_size):
* Scripts/webkitpy/benchmark_runner/browser_driver/linux_chrome_driver.py: Copied from Tools/Scripts/webkitpy/benchmark_runner/browser_driver/gtk_minibrowser_driver.py.
(LinuxChromeDriver):
(LinuxChromeDriver.launch_url):
* Scripts/webkitpy/benchmark_runner/browser_driver/linux_epiphany_driver.py: Renamed from Tools/Scripts/webkitpy/benchmark_runner/browser_driver/gtk_browser_driver.py.
(EpiphanyBrowserDriver):
(EpiphanyBrowserDriver.launch_url):
* Scripts/webkitpy/benchmark_runner/browser_driver/linux_firefox_driver.py: Copied from Tools/Scripts/webkitpy/benchmark_runner/browser_driver/gtk_minibrowser_driver.py.
(LinuxFirefoxDriver):
(LinuxFirefoxDriver.launch_url):
* Scripts/webkitpy/benchmark_runner/browser_driver/linux_minibrowsergtk_driver.py: Renamed from Tools/Scripts/webkitpy/benchmark_runner/browser_driver/gtk_minibrowser_driver.py.
(GTKMiniBrowserDriver):
(GTKMiniBrowserDriver.launch_url):
* Scripts/webkitpy/benchmark_runner/http_server_driver/simple_http_server_driver.py:
(SimpleHTTPServerDriver):
* Scripts/webkitpy/benchmark_runner/run_benchmark.py:
(getplatform):
(getdefaultbrowser):
(parse_args):
* Scripts/webkitpy/benchmark_runner/utils.py:
(load_subclasses): The loading of subclasses was still (even after r196979) sensitive to the order in which the modules are loaded.
We have to ensure that the files containing subclasses of the base_class_file are loaded after the base_class_file,
we can do that by matching against the base_class_file pattern when the list is created.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@209090 268f45cc-cd09-0410-ab3c-d52691b4dbfc