Clean up dns prefetch code, and also port it.
- remove slave threads and use HostResolver in asynchronous mode instead (while still limiting number of concurrent lookups)
- make the implementation portable and make DnsMaster unit test compile and pass on Linux
- add more tests to DnsMaster unit test to simulate various shutdown scenarios, concurrent lookups, and to verify that we don't exceed our limit of concurrent lookup requests)
- remove some tests which relied on specifics of slaves' inner working
Bonus: shutdown is almost instant now, no need to have a timeout.
BUG=5687, 6683
Review URL: http://codereview.chromium.org/15076
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@9312 0039d316-1c4b-4281-b951-d872f2087c98
13 files changed
