[net/dns] Serve requests from HOSTS file if possible.

net/base/host_resolver_impl.h

Index: net/base/host_resolver_impl.h
diff --git a/net/base/host_resolver_impl.h b/net/base/host_resolver_impl.h
index dd8c70e334c285d75ff72691e1a5e0c51b9e10b4..348e6ef949419e9586c2d75845bfd5deb8210115 100644
--- a/net/base/host_resolver_impl.h
+++ b/net/base/host_resolver_impl.h
@@ -27,6 +27,7 @@
 
 namespace net {
 
+class DnsSession;
 class DnsTransactionFactory;
 
 // For each hostname that is requested, HostResolver creates a
@@ -184,10 +185,15 @@ class NET_EXPORT HostResolverImpl
   // if it is a positive entry.
   bool ServeFromCache(const Key& key,
                       const RequestInfo& info,
-                      const BoundNetLog& request_net_log,
                       int* net_error,
                       AddressList* addresses);
 
+  // If |key| is not found in the HOSTS file or no HOSTS file known, returns
+  // false, otherwise returns true and fills |addresses|.
+  bool ServeFromHosts(const Key& key,
+                      const RequestInfo& info,
+                      AddressList* addresses);
+
   // Notifies IPv6ProbeJob not to call back, and discard reference to the job.
   void DiscardIPv6ProbeJob();
 
@@ -212,6 +218,9 @@ class NET_EXPORT HostResolverImpl
   // Might start new jobs.
   void AbortAllInProgressJobs();
 
+  // Attempts to serve each Job in |jobs_| from the HOSTS file.
+  void TryServingAllJobsFromHosts();
+
   // NetworkChangeNotifier::IPAddressObserver:
   virtual void OnIPAddressChanged() OVERRIDE;
 
@@ -241,6 +250,7 @@ class NET_EXPORT HostResolverImpl
   // Address family to use when the request doesn't specify one.
   AddressFamily default_address_family_;
 
+  scoped_refptr<DnsSession> dns_session_;
   scoped_ptr<DnsConfigService> dns_config_service_;
 
   // Indicate if probing is done after each network change event to set address