Move AsyncDns field trial to server-side control.

chrome/browser/net/async_dns_field_trial.h

Index: chrome/browser/net/async_dns_field_trial.h
diff --git a/chrome/browser/net/async_dns_field_trial.h b/chrome/browser/net/async_dns_field_trial.h
index 48b3945fb0bbebb5ba12d46d17553abcbaf813cb..141db3250e73eb9adc8d2c444a4cdaa08c984a3e 100644
--- a/chrome/browser/net/async_dns_field_trial.h
+++ b/chrome/browser/net/async_dns_field_trial.h
@@ -5,17 +5,9 @@
 #ifndef CHROME_BROWSER_NET_ASYNC_DNS_FIELD_TRIAL_H_
 #define CHROME_BROWSER_NET_ASYNC_DNS_FIELD_TRIAL_H_
 
-#include <string>
-
-class CommandLine;
-class Profile;
-
 namespace chrome_browser_net {
 
-// Configures the AsyncDns field trial as follows.
-// group A (async disabled): use CreateSystemHostResolver
-// group B (async enabled):  use CreateAsyncHostResolver
-// Returns true if should use CreateAsyncHostResolver.
+// Returns true when the async resolver should be used.
 bool ConfigureAsyncDnsFieldTrial();
 
 }  // namespace chrome_browser_net