Clean up build targets for layout bots, add dcheck_always_on to release builds.
Clean up build targets for layout bots, add dcheck_always_on to release builds.

R=thakis@chromium.org, iannucci@chromium.org
BUG=237021

Review URL: https://chromiumcodereview.appspot.com/15028020

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@199511 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build