Move the user agent styles sheets to blink_resources.grd (Part 3)

Blink should make use of blink_resources.grd for the inline resources of user agent stylesheets.
This removes the dependency upon using make-file-arrays.py which embeds these resources as strings. 

Also the .rodata section of libblink_web (in component build mode) is reduced by ~33kb.

Part 1: https://codereview.chromium.org/436843004/
Part 2: https://codereview.chromium.org/422023008
Part 2 Unit Test support: https://codereview.chromium.org/456413002/

BUG=312586

Review URL: https://codereview.chromium.org/438843004

git-svn-id: svn://svn.chromium.org/blink/trunk@181917 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove unused python version checker script
    
The ensure-valid-python script seems to be unused,
and additionally in webkitpy there is already another
version checker implementation.

BUG=none

Review URL: https://codereview.chromium.org/559993002

git-svn-id: svn://svn.chromium.org/blink/trunk@181918 bbb929c8-8fbe-4397-9dbb-9b2b20218538