DevTools: Fix inaccurate timeout handling with skipAllPauses.

Bug repro:
- click long resume button to resume with disabled breakpoints for 500 ms
- hit Ctrl+R immediately, so that we send to backend setSkipAllPauses(true,true)
- may well happen that the callback from step 1 would enable breakpoints before the page reloads

BUG=115105
R=pfeldman,vsevik, johnjbarton@chromium.org

Review URL: https://codereview.chromium.org/25011003

git-svn-id: svn://svn.chromium.org/blink/trunk@158560 bbb929c8-8fbe-4397-9dbb-9b2b20218538