Refactoring: Add an Event factory function to create a simple event.

It's equivalent to Event::create(name, false, false).
http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#fire-a-simple-event

BUG=none
TEST=none; no behavior changes.

Review URL: https://chromiumcodereview.appspot.com/23449003

git-svn-id: svn://svn.chromium.org/blink/trunk@156804 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Refactoring: execute, isEnabled, state, value functions of EditorInternalCommand class should take a Frame reference argument.

They are always non-null. On the other hand, the frame argument of
isSupportedFromDOM can be null.

BUG=none
TEST=none; no behavior changes.

Review URL: https://chromiumcodereview.appspot.com/23532002

git-svn-id: svn://svn.chromium.org/blink/trunk@156805 bbb929c8-8fbe-4397-9dbb-9b2b20218538