Revert 89605 - Support automatic javascript test registry in gtest when creating WebUI tests.

Revert 89605 - Support automatic javascript test registry in gtest when creating WebUI tests.

The goal was to support something as simple as the following, where the tests in the
javascript files would be 1st class GTESTs, supporting FLAKY_, DISABLED_, etc, and
registered at linker_initialization time.

WEB_UI_BROWSER_TEST_JS(WebUIBrowserTest, TestJSPass,
                       FILE_PATH_LITERAL("sample_passing.js")) {
  ui_test_utils::NavigateToURL(browser(), GURL(chrome::kChromeUIDownloadsURL));
}

WEB_UI_BROWSER_TEST_JS_FALSE(WebUIBrowserTest, TestJSFail,
                             FILE_PATH_LITERAL("sample_failing.js")) {
  ui_test_utils::NavigateToURL(browser(), GURL(chrome::kChromeUIDownloadsURL));
}

http://www.chromium.org/Home/domui-testing

In order to support linker init time, I had to modify path_service to support
Unregistration, and chrome_paths to allow multiple invocations.

BUG=82437
R=estade@chromium.org,jhawkins@chromium.org
TEST=browser_tests --gtest_filter=WebUIBrowserTest*

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=89453

Review URL: http://codereview.chromium.org/7087014

TBR=scr@chromium.org
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=89607