Unindent some class declarations in workers/

Be consistent and follow Blink style of not indenting declarations
inside a namespace scope.

R=haraken
BUG=

Review URL: https://codereview.chromium.org/642013002

git-svn-id: svn://svn.chromium.org/blink/trunk@183456 bbb929c8-8fbe-4397-9dbb-9b2b20218538