Fix various issues with Markdown docs

- Removed links to old wiki pages
- Fixed broken table in test_descriptions.md
- Fixed tables that don't have heading
- Fix codeblock in common_build_tasks.md

Review URL: https://codereview.chromium.org/1473953002

Cr-Commit-Position: refs/heads/master@{#361773}
diff --git a/docs/linux_debugging.md b/docs/linux_debugging.md
index 822c23d9..058391d 100644
--- a/docs/linux_debugging.md
+++ b/docs/linux_debugging.md
@@ -439,8 +439,7 @@
 
 See
 https://sites.google.com/a/chromium.org/dev/developers/profiling-chromium-and-webkit
-and
-http://code.google.com/p/chromium/wiki/LinuxProfiling
+and [Linux Profiling](linux_profiling.md).
 
 ## i18n