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

1 files changed, 5 insertions, 6 deletions

diff --git a/chrome/browser/net/dns_host_info.h b/chrome/browser/net/dns_host_info.h
index 50c44f3..b9ea157 100644
--- a/chrome/browser/net/dns_host_info.h
+++ b/chrome/browser/net/dns_host_info.h
@@ -4,9 +4,8 @@
 
 // A DnsHostInfo object is used to store status of a Dns lookup of a specific
 // hostname.
-// It includes progress, from placement in the DnsMaster's queue, to assignment
-// to a slave, to resolution by the (blocking) DNS service as either FOUND or
-// NO_SUCH_NAME.
+// It includes progress, from placement in the DnsMaster's queue, to resolution
+// by the DNS service as either FOUND or NO_SUCH_NAME.
 
 #ifndef CHROME_BROWSER_NET_DNS_HOST_INFO_H_
 #define CHROME_BROWSER_NET_DNS_HOST_INFO_H_
@@ -54,9 +53,9 @@ class DnsHostInfo {
   enum DnsProcessingState {
       // When processed by our prefetching system, the states are:
       PENDING,       // Constructor has completed.
-      QUEUED,        // In prefetch queue but not yet assigned to a slave.
-      ASSIGNED,      // Currently being processed by a slave.
-      ASSIGNED_BUT_MARKED,  // Needs to be deleted as soon as slave is done.
+      QUEUED,        // In prefetch queue but not yet being resolved.
+      ASSIGNED,      // Currently being processed.
+      ASSIGNED_BUT_MARKED,  // Needs to be deleted as soon as it's resolved.
       FOUND,         // DNS prefetch search completed.
       NO_SUCH_NAME,  // DNS prefetch search completed.
       // When processed by the network stack during navigation, the states are: