Replacing window.cancelTimeout with clearTimeout
Replacing window.cancelTimeout with clearTimeout

Summary: window.cancelTimeout doesn't exist.

Test Plan:
Verified in Chrome console that clearTimeout exists
but not window.cancelTimeout

Reviewers: mkedia, haoyi, kylec

Reviewed By: kylec

Subscribers: changesbot, mkedia

Differential Revision: https://tails.corp.dropbox.com/D127585

dropbox/changes,wfxiang08/changes,wfxiang08/changes,wfxiang08/changes,bowlofstew/changes,dropbox/changes,wfxiang08/changes,dropbox/changes,bowlofstew/changes,bowlofstew/changes,bowlofstew/changes,dropbox/changes