DevTools: Introduce an experimental setting to open console with Ctrl+Tilde, not Esc.

Drive-by: Fix console in drawer behavior so that it could be opened back while it is closing.

R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/22586002

git-svn-id: svn://svn.chromium.org/blink/trunk@156559 bbb929c8-8fbe-4397-9dbb-9b2b20218538