Introduce ERR_NETWORK_CHANGED and allow URLFetcher to automatically retry on that error.

net/base/host_resolver_impl.cc

Index: net/base/host_resolver_impl.cc
diff --git a/net/base/host_resolver_impl.cc b/net/base/host_resolver_impl.cc
index b56524ca8ad73ad438b63833e55710d03abeac20..2d546c548221b2ad80df5760eac3c3847455541c 100644
--- a/net/base/host_resolver_impl.cc
+++ b/net/base/host_resolver_impl.cc
@@ -1269,9 +1269,9 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
 
   // Called from AbortAllInProgressJobs. Completes all requests as aborted
   // and destroys the job.
-  void Abort() {
+  void Abort(int error) {
     DCHECK(is_running());
-    CompleteRequestsWithError(ERR_ABORTED);
+    CompleteRequestsWithError(error);
   }
 
   // If DnsTask present, abort it and fall back to ProcTask.
@@ -1532,6 +1532,7 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
     }
 
     bool did_complete = (entry.error != ERR_ABORTED) &&
+                        (entry.error != ERR_NETWORK_CHANGED) &&
                         (entry.error != ERR_HOST_RESOLVER_QUEUE_TOO_LARGE);
     if (did_complete)
       resolver_->CacheResult(key_, entry, ttl);
@@ -2032,7 +2033,7 @@ HostResolverImpl::Key HostResolverImpl::GetEffectiveKeyForRequest(
   return Key(info.hostname(), effective_address_family, effective_flags);
 }
 
-void HostResolverImpl::AbortAllInProgressJobs() {
+void HostResolverImpl::AbortAllInProgressJobs(int error) {
   // In Abort, a Request callback could spawn new Jobs with matching keys, so
   // first collect and remove all running jobs from |jobs_|.
   ScopedVector<Job> jobs_to_abort;
@@ -2055,7 +2056,7 @@ void HostResolverImpl::AbortAllInProgressJobs() {
 
   // Then Abort them.
   for (size_t i = 0; self && i < jobs_to_abort.size(); ++i) {
-    jobs_to_abort[i]->Abort();
+    jobs_to_abort[i]->Abort(error);
     jobs_to_abort[i] = NULL;
   }
 }
@@ -2088,7 +2089,7 @@ void HostResolverImpl::OnIPAddressChanged() {
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
   new LoopbackProbeJob(probe_weak_ptr_factory_.GetWeakPtr());
 #endif
-  AbortAllInProgressJobs();
+  AbortAllInProgressJobs(ERR_NETWORK_CHANGED);
   // |this| may be deleted inside AbortAllInProgressJobs().
 }
 
@@ -2126,7 +2127,7 @@ void HostResolverImpl::OnDNSChanged() {
 
   // Existing jobs will have been sent to the original server so they need to
   // be aborted.
-  AbortAllInProgressJobs();
+  AbortAllInProgressJobs(ERR_NETWORK_CHANGED);
 
   // |this| may be deleted inside AbortAllInProgressJobs().
   if (self)