Rename symbols including "LayoutTest" in Blink C++ code

- LayoutTestSupport -> WebTestSupport
 - IsRunningLayoutTest() -> IsRunningWebTest()
 - SetIsRunningWebTest() -> SetIsRunningWebTest()
- kLayoutTestResourcesDir -> kWebTestsResourcesDir
- LayoutTestsFilePath() -> WebTestsFilePath()
- BlinkLayoutTestsDir() -> BlinkWebTestsDir()

Change-Id: If31f8d73f795d4271ccec76f51182a18c891fb30
Bug: 843412
Reviewed-on: https://chromium-review.googlesource.com/c/1352116
Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611524}
46 files changed