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

net/base/host_resolver.h

Index: net/base/host_resolver.h
diff --git a/net/base/host_resolver.h b/net/base/host_resolver.h
index e375961f47db81cf5382ca832e870bb4764a57b8..a282701e6b4aae7eec4b310fcc25f201065953be 100644
--- a/net/base/host_resolver.h
+++ b/net/base/host_resolver.h
@@ -132,10 +132,10 @@ class NET_EXPORT HostResolver {
                       RequestHandle* out_req,
                       const BoundNetLog& net_log) = 0;
 
-  // Resolves the given hostname (or IP address literal) out of cache
-  // only.  This is guaranteed to complete synchronously.  This acts like
-  // |Resolve()| if the hostname is IP literal or cached value exists.
-  // Otherwise, ERR_DNS_CACHE_MISS is returned.
+  // Resolves the given hostname (or IP address literal) out of cache or HOSTS
+  // file (if enabled) only. This is guaranteed to complete synchronously.
+  // This acts like |Resolve()| if the hostname is IP literal, or cached value
+  // or HOSTS entry exists. Otherwise, ERR_DNS_CACHE_MISS is returned.
   virtual int ResolveFromCache(const RequestInfo& info,
                                AddressList* addresses,
                                const BoundNetLog& net_log) = 0;