[fsp] Initial implementation of timeout logic for requests.

This patch introduces a basic mechanism for timing out stale requests.
If none of callbacks are called within a fixed amount of time, then the request
is considered as stale, and aborted with an FILE_ERROR_ABORT error code.

TEST=unit_test: FileSystemProviderRequestManagerTest.AbortOnTimeout
BUG=248427

Review URL: https://codereview.chromium.org/241673005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@264773 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed