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/README.md b/docs/README.md
index 04b09b743..915d1aa9 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -145,20 +145,19 @@
     work.
 
 ### Testing
-*   [Running and Debugging Layout Tests](testing/layout_tests.md)
-*   [Writing Layout Tests](testing/writing_layout_tests.md) - Layout Tests using
+*   [Running and Debugging Web Tests](testing/web_tests.md)
+*   [Writing Web Tests](testing/writing_web_tests.md) - Web Tests using
     `content_shell`
-*   [Layout Test Expectations and Baselines](testing/layout_test_expectations.md) -
-    Setting expected results of layout tests.
-*   [Layout Tests Tips](testing/layout_tests_tips.md) - Best practices for Layout
-    Tests
-*   [Layout Tests with Manual Fallback](testing/layout_tests_with_manual_fallback.md) -
+*   [Web Test Expectations and Baselines](testing/web_test_expectations.md) -
+    Setting expected results of web tests.
+*   [Web Tests Tips](testing/web_tests_tips.md) - Best practices for web tests
+*   [Web Tests with Manual Fallback](testing/webt_tests_with_manual_fallback.md) -
     Writing tests that simulate manual interventions
-*   [Extending the Layout Test Framework](how_to_extend_layout_test_framework.md)
-*   [Fixing Layout Test Flakiness](testing/identifying_tests_that_depend_on_order.md) -
-    Diagnosing and fixing layout test flakiness due to ordering dependencies.
-*   [Running Layout Tests using `content_shell`](testing/layout_tests_in_content_shell.md) -
-    Running layout tests by hand.
+*   [Extending the Web Test Framework](how_to_extend_web_test_framework.md)
+*   [Fixing Web Test Flakiness](testing/identifying_tests_that_depend_on_order.md) -
+    Diagnosing and fixing web test flakiness due to ordering dependencies.
+*   [Running Web Tests using `content_shell`](testing/web_tests_in_content_shell.md) -
+    Running web tests by hand.
 *   [Web Platform Tests](testing/web_platform_tests.md) - Shared tests across
     browser vendors
 *   [Using Breakpad with `content_shell`](testing/using_breakpad_with_content_shell.md) -
@@ -217,8 +216,8 @@
     isolate browser components with different privileges.
 *   [Zygote Process](linux_zygote.md) - How the Linux Zygote process, used to
     spawn new processes, works.
-*   [Running Layout Tests on Linux](layout_tests_linux.md) - Linux-specific
-    instructions for running layout tests.
+*   [Running Web Tests on Linux](web_tests_linux.md) - Linux-specific
+    instructions for running web tests.
 *   [Linux Sysroot Images](linux_sysroot.md) - How builds use libraries on Linux
 *   [Linux Hardware Video Decoding](linux_hw_video_decode.md) - Enabling
     hardware video decode codepaths on Linux