Remove unused WorkerGlobalScope::Observer interface.

No one implements it.

BUG=none
TEST=none; no behavior changes

Review URL: https://codereview.chromium.org/173503006

git-svn-id: svn://svn.chromium.org/blink/trunk@167599 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Prefactorings for filter suggest box.

See https://chromiumcodereview.appspot.com/59843002/

BUG=

Review URL: https://codereview.chromium.org/169843003

git-svn-id: svn://svn.chromium.org/blink/trunk@167600 bbb929c8-8fbe-4397-9dbb-9b2b20218538