DevTools: revert r156210 for breaking styles sidebar (it has no colors).

TBR=lushnikov

BUG=275738

Review URL: https://chromiumcodereview.appspot.com/23064018

git-svn-id: svn://svn.chromium.org/blink/trunk@156334 bbb929c8-8fbe-4397-9dbb-9b2b20218538