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

- adjust initialization and shutdown of dns prefetching (now it relies on the IO message loop being present)

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@10021 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 3 insertions, 4 deletions

diff --git a/net/base/host_resolver.h b/net/base/host_resolver.h
index bfae53c..6e61eb5 100644
--- a/net/base/host_resolver.h
+++ b/net/base/host_resolver.h
@@ -41,10 +41,9 @@ class HostResolver {
   //
   // When callback is null, the operation completes synchronously.
   //
-  // When callback is non-null, ERR_IO_PENDING is returned if the operation
-  // could not be completed synchronously, in which case the result code will
-  // be passed to the callback when available.
-  //
+  // When callback is non-null, the operation will be performed asynchronously.
+  // ERR_IO_PENDING is returned if it has been scheduled successfully. Real
+  // result code will be passed to the completion callback.
   int Resolve(const std::string& hostname, int port,
               AddressList* addresses, CompletionCallback* callback);