Fix various issues with Markdown docs

docs/linux_debugging.md

 # Tips for debugging on Linux
 
 This page is for Chromium-specific debugging tips; learning how to run gdb is
 out of scope.
 
 [TOC]
 
 ## Symbolized stack trace
 
 The sandbox can interfere with the internal symbolizer. Use `--no-sandbox` (but
@@ skipping 421 matching lines @@
 
     $ cd $CHROMIUM_ROOT/src
     $ build/gyp_chromium -Duse_allocator=none
 
 and rebuild.
 
 ## Profiling
 
 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
 
 We obey your system locale. Try something like:
 
     LANG=ja_JP.UTF-8 out/Debug/chrome
 
 If this doesn't work, make sure that the `LANGUAGE`, `LC_ALL` and `LC_MESSAGE`
 environment variables aren't set -- they have higher priority than LANG in the
 order listed. Alternatively, just do this:
@@ skipping 85 matching lines @@
 [Running layout tests on Linux](layout_tests_linux.md) page.
 
 If you need to test something with hardware accelerated compositing
 (e.g., compiz), you can use `Xgl` (`sudo apt-get install xserver-xgl`). E.g.:
 
     Xgl :1 -ac -accel glx:pbuffer -accel xv:pbuffer -screen 1024x768
 
 ## Mozilla Tips
 
 https://developer.mozilla.org/en/Debugging_Mozilla_on_Linux_FAQ