[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..7b0900fb0a478a503afd4ca4173207f0e7e84a18 100644
--- a/net/base/host_resolver_impl.h
+++ b/net/base/host_resolver_impl.h
@@ -23,12 +23,11 @@
 #include "net/base/net_log.h"
 #include "net/base/network_change_notifier.h"
 #include "net/base/prioritized_dispatcher.h"
+#include "net/dns/dns_client.h"
 #include "net/dns/dns_config_service.h"
 
 namespace net {
 
-class DnsTransactionFactory;
-
 // For each hostname that is requested, HostResolver creates a
 // HostResolverImpl::Job. When this job gets dispatched it creates a ProcTask
 // which runs the given HostResolverProc on a WorkerPool thread. If requests for
@@ -154,6 +153,8 @@ class NET_EXPORT HostResolverImpl
   }
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(HostResolverImplTest, DnsTask);
+  FRIEND_TEST_ALL_PREFIXES(HostResolverImplTest, ServeFromHosts);
   class Job;
   class ProcTask;
   class IPv6ProbeJob;
@@ -163,10 +164,14 @@ class NET_EXPORT HostResolverImpl
   typedef std::map<Key, Job*> JobMap;
   typedef std::vector<Request*> RequestsList;
 
+  void set_dns_client_for_tests(scoped_ptr<DnsClient> client) {
+    dns_client_ = client.Pass();
+  }
+
   // Helper used by |Resolve()| and |ResolveFromCache()|.  Performs IP
-  // literal and cache lookup, returns OK if successful,
+  // literal, cache and HOSTS lookup (if enabled), returns OK if successful,
   // ERR_NAME_NOT_RESOLVED if either hostname is invalid or IP literal is
-  // incompatible, ERR_DNS_CACHE_MISS if entry was not found in cache.
+  // incompatible, ERR_DNS_CACHE_MISS if entry was not found in cache and HOSTS.
   int ResolveHelper(const Key& key,
                     const RequestInfo& info,
                     AddressList* addresses,
@@ -184,10 +189,15 @@ 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 +222,9 @@ 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;
 
@@ -221,6 +234,9 @@ class NET_EXPORT HostResolverImpl
   // DnsConfigService::Observer:
   virtual void OnConfigChanged(const DnsConfig& dns_config) OVERRIDE;
 
+  // True if have fully configured DNS client.
+  bool HaveDnsConfig() const;
+
   // Cache of host resolution results.
   scoped_ptr<HostCache> cache_;
 
@@ -236,11 +252,10 @@ class NET_EXPORT HostResolverImpl
   // Parameters for ProcTask.
   ProcTaskParams proc_params_;
 
-  scoped_ptr<DnsTransactionFactory> dns_transaction_factory_;
-
   // Address family to use when the request doesn't specify one.
   AddressFamily default_address_family_;
 
+  scoped_ptr<DnsClient> dns_client_;
   scoped_ptr<DnsConfigService> dns_config_service_;
 
   // Indicate if probing is done after each network change event to set address