[NetworkChangeNotifier] Run Windows connection type computation on other thread

net/base/network_change_notifier_win.cc

Index: net/base/network_change_notifier_win.cc
diff --git a/net/base/network_change_notifier_win.cc b/net/base/network_change_notifier_win.cc
index 9b2b35ec76bfbc08a1ac6008dbf9f85b80a2618b..94efd29f5c662548ea71b86544e0ef26d7cd7bdd 100644
--- a/net/base/network_change_notifier_win.cc
+++ b/net/base/network_change_notifier_win.cc
@@ -14,6 +14,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
+#include "base/task_runner_util.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
@@ -59,6 +60,8 @@ NetworkChangeNotifierWin::NetworkChangeNotifierWin()
       last_computed_connection_type_(RecomputeCurrentConnectionType()),
       last_announced_offline_(last_computed_connection_type_ ==
                               CONNECTION_NONE),
+      calculate_connection_type_(base::BindRepeating(
+          &NetworkChangeNotifierWin::RecomputeCurrentConnectionType)),
       weak_factory_(this) {
   memset(&addr_overlapped_, 0, sizeof addr_overlapped_);
   addr_overlapped_.hEvent = WSACreateEvent();
@@ -134,10 +137,9 @@ NetworkChangeNotifierWin::NetworkChangeCalculatorParamsWin() {
 // experiments I ran... However none of them correctly returned "offline" when
 // executing 'ipconfig /release'.
 //
+// static
 NetworkChangeNotifier::ConnectionType
-NetworkChangeNotifierWin::RecomputeCurrentConnectionType() const {
-  DCHECK(CalledOnValidThread());
-
+NetworkChangeNotifierWin::RecomputeCurrentConnectionType() {
   EnsureWinsockInit();
 
   // The following code was adapted from:
@@ -201,8 +203,7 @@ NetworkChangeNotifierWin::RecomputeCurrentConnectionType() const {
       << "WSALookupServiceEnd() failed with: " << result;
 
   // TODO(droger): Return something more detailed than CONNECTION_UNKNOWN.
-  return found_connection ? ConnectionTypeFromInterfaces()
-                          : NetworkChangeNotifier::CONNECTION_NONE;
+  return found_connection ? ConnectionTypeFromInterfaces() : CONNECTION_NONE;
 }
 
 NetworkChangeNotifier::ConnectionType
@@ -224,13 +225,17 @@ void NetworkChangeNotifierWin::OnObjectSignaled(HANDLE object) {
 
   // Start watching for the next address change.
   WatchForAddressChange();
+  DCHECK(dns_task_runner_);
 
-  NotifyObservers();
+  base::PostTaskAndReplyWithResult(
+      dns_task_runner_.get(), FROM_HERE, calculate_connection_type_,
+      base::Bind(&NetworkChangeNotifierWin::NotifyObservers,
+                 weak_factory_.GetWeakPtr()));

[pauljensen, 2017/05/23 17:57:40]

do we need to use a weakptr if NCNWin is guaranteed to outlive dns thread?

[jkarlin, 2017/05/23 18:02:15]

see previous response.

 }
 
-void NetworkChangeNotifierWin::NotifyObservers() {
+void NetworkChangeNotifierWin::NotifyObservers(ConnectionType connection_type) {
   DCHECK(CalledOnValidThread());
-  SetCurrentConnectionType(RecomputeCurrentConnectionType());
+  SetCurrentConnectionType(connection_type);
   NotifyObserversOfIPAddressChange();
 
   // Calling GetConnectionType() at this very moment is likely to give
@@ -241,6 +246,8 @@ void NetworkChangeNotifierWin::NotifyObservers() {
   // If after one second we determine we are still offline, we will
   // delay again.
   offline_polls_ = 0;
+  // TODO(jkarlin): I'm not sure that calling with 'this' is safe. Can it be
+  // deleted?
   timer_.Start(FROM_HERE, base::TimeDelta::FromSeconds(1), this,
                &NetworkChangeNotifierWin::NotifyParentOfConnectionTypeChange);
 }
@@ -274,8 +281,12 @@ void NetworkChangeNotifierWin::WatchForAddressChange() {
   // Treat the transition from NotifyAddrChange failing to succeeding as a
   // network change event, since network changes were not being observed in
   // that interval.
-  if (sequential_failures_ > 0)
-    NotifyObservers();
+  if (sequential_failures_ > 0) {
+    base::PostTaskAndReplyWithResult(
+        dns_task_runner_.get(), FROM_HERE, calculate_connection_type_,
+        base::Bind(&NetworkChangeNotifierWin::NotifyObservers,
+                   weak_factory_.GetWeakPtr()));
+  }
 
   if (sequential_failures_ < 2000) {
     UMA_HISTOGRAM_COUNTS_10000("Net.NotifyAddrChangeFailures",
@@ -292,6 +303,9 @@ bool NetworkChangeNotifierWin::WatchForAddressChangeInternal() {
   if (!dns_config_service_thread_->IsRunning()) {
     dns_config_service_thread_->StartWithOptions(
       base::Thread::Options(base::MessageLoop::TYPE_IO, 0));
+    if (!dns_task_runner_)
+      dns_task_runner_ =
+          dns_config_service_thread_->message_loop()->task_runner();
   }
 
   ResetEventIfSignaled(addr_overlapped_.hEvent);
@@ -305,7 +319,16 @@ bool NetworkChangeNotifierWin::WatchForAddressChangeInternal() {
 }
 
 void NetworkChangeNotifierWin::NotifyParentOfConnectionTypeChange() {
-  SetCurrentConnectionType(RecomputeCurrentConnectionType());
+  base::PostTaskAndReplyWithResult(
+      dns_task_runner_.get(), FROM_HERE, calculate_connection_type_,
+      base::Bind(
+          &NetworkChangeNotifierWin::NotifyParentOfConnectionTypeChangeImpl,
+          weak_factory_.GetWeakPtr()));
+}
+
+void NetworkChangeNotifierWin::NotifyParentOfConnectionTypeChangeImpl(
+    ConnectionType connection_type) {
+  SetCurrentConnectionType(connection_type);
   bool current_offline = IsOffline();
   offline_polls_++;
   // If we continue to appear offline, delay sending out the notification in
@@ -323,10 +346,10 @@ void NetworkChangeNotifierWin::NotifyParentOfConnectionTypeChange() {
 
   NotifyObserversOfConnectionTypeChange();
   double max_bandwidth_mbps = 0.0;
-  ConnectionType connection_type = CONNECTION_NONE;
+  ConnectionType max_connection_type = CONNECTION_NONE;
   GetCurrentMaxBandwidthAndConnectionType(&max_bandwidth_mbps,
-                                          &connection_type);
-  NotifyObserversOfMaxBandwidthChange(max_bandwidth_mbps, connection_type);
+                                          &max_connection_type);
+  NotifyObserversOfMaxBandwidthChange(max_bandwidth_mbps, max_connection_type);
 }
 
 }  // namespace net