Update "LayoutTests" / "layout test" in docs/*.md.

This CL renames the following md files:
 - layout_tests_linux -> web_tests_linux.md
 - how_to_extend_layout_test_framework.md ->
   how_to_extend_web_test_framework.md
 - testing/layout_test_baseline_fallback.md ->
   testing/web_test_baseline_fallback.md
 - testing/layout_test_expectations.md -> testing/web_test_expectations.md
 - testing/layout_tests.md -> testing/web_tests.md
 - testing/layout_tests_in_content_shell.md ->
   testing/web_tests_in_content_shell.md
 - testing/layout_tests_tips.md -> testing/web_tests_tips.md
 - testing/layout_tests_with_manual_fallback.md ->
   testing/web_tests_with_manual_fallback.md
 - testing/writing_layout_tests -> testing/writing_web_tests.md

No-Try: true
Change-Id: Ied34815c92e449888b20818540a5ed0a76107bd1
Bug: 843412
Reviewed-on: https://chromium-review.googlesource.com/c/1350559
Commit-Queue: Kent Tamura <[email protected]>
Reviewed-by: Quinten Yearsley <[email protected]>
Cr-Commit-Position: refs/heads/master@{#611024}
diff --git a/docs/using_a_linux_chroot.md b/docs/using_a_linux_chroot.md
index a8f4304..0ebb7ec 100644
--- a/docs/using_a_linux_chroot.md
+++ b/docs/using_a_linux_chroot.md
@@ -1,6 +1,6 @@
 # Using a chroot
 
-If you want to run layout tests and you're not running Lucid, you'll get errors
+If you want to run web tests and you're not running Lucid, you'll get errors
 due to version differences in libfreetype. To work around this, you can use a
 chroot.
 
@@ -65,16 +65,16 @@
 ### Running X apps
 
 I also have `DISPLAY=:0` in my `$debian_chroot` section so I can run test_shell
-or layout tests without manually setting my display every time.  Your display
+or web tests without manually setting my display every time.  Your display
 number may vary (`echo $DISPLAY` outside the chroot to see what your display
 number is).
 
 You can also use `Xvfb` if you only want to
-[run tests headless](layout_tests_linux.md#Using-an-embedded-X-server).
+[run tests headless](web_tests_linux.md#Using-an-embedded-X-server).
 
-### Having layout test results open in a browser
+### Having web test results open in a browser
 
-After running layout tests, you should get a new browser tab or window that
+After running web tests, you should get a new browser tab or window that
 opens results.html.  If you get an error "Failed to open
 file:///path/to/results.html, check the
 following conditions.