arc: Reduce logspam when ARC is not enabled/available

components/arc/net/arc_net_host_impl.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/arc/net/arc_net_host_impl.h"
 
 #include <string>
 #include <utility>
 #include <vector>
 
@@ skipping 275 matching lines @@
   LOG(ERROR) << "Failed to query default logical network";
 }
 
 }  // namespace
 
 namespace arc {
 
 ArcNetHostImpl::ArcNetHostImpl(ArcBridgeService* bridge_service)
     : ArcService(bridge_service), binding_(this), weak_factory_(this) {
   arc_bridge_service()->net()->AddObserver(this);
-  GetStateHandler()->AddObserver(this, FROM_HERE);
 }
 
 ArcNetHostImpl::~ArcNetHostImpl() {
   DCHECK(thread_checker_.CalledOnValidThread());
   arc_bridge_service()->net()->RemoveObserver(this);
-  if (chromeos::NetworkHandler::IsInitialized()) {
+  if (observing_network_state_) {

[Yusuke Sato, 2016/11/30 23:29:39]

Do we need the check? I think the convention in Chromium is that
RemoveObserver(p) is no-op when |p| is not in the list.

[Luis Héctor Chávez, 2016/11/30 23:45:08]

Yes, but
https://cs.chromium.org/chromium/src/chromeos/network/network_state_handler.c...
also does logging. It might be a bit confusing for the log readers to see that
something is unregistering but never registering for event notification.

[Yusuke Sato, 2016/11/30 23:59:30]

Acknowledged.

     GetStateHandler()->RemoveObserver(this, FROM_HERE);
   }
 }
 
 void ArcNetHostImpl::OnInstanceReady() {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   mojom::NetHostPtr host;
   binding_.Bind(GetProxy(&host));
   auto* instance = arc_bridge_service()->net()->GetInstanceForMethod("Init");
   DCHECK(instance);
   instance->Init(std::move(host));
+
+  if (chromeos::NetworkHandler::IsInitialized()) {
+    GetStateHandler()->AddObserver(this, FROM_HERE);
+    observing_network_state_ = true;
+  }
+}
+
+void ArcNetHostImpl::OnInstanceClosed() {
+  if (!observing_network_state_)

[Yusuke Sato, 2016/11/30 23:29:39]

same

+    return;
+
+  GetStateHandler()->RemoveObserver(this, FROM_HERE);
+  observing_network_state_ = false;
 }
 
 void ArcNetHostImpl::GetNetworksDeprecated(
     bool configured_only,
     bool visible_only,
     const GetNetworksDeprecatedCallback& callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (configured_only && visible_only) {
     VLOG(1) << "Illegal arguments - both configured and visible networks "
                "requested.";
@@ skipping 315 matching lines @@
       "WifiEnabledStateChanged", kWifiEnabledStateChanged);
   if (!net_instance)
     return;
 
   bool is_enabled = GetStateHandler()->IsTechnologyEnabled(
       chromeos::NetworkTypePattern::WiFi());
   net_instance->WifiEnabledStateChanged(is_enabled);
 }
 
 void ArcNetHostImpl::OnShuttingDown() {
+  DCHECK(observing_network_state_);

[Yusuke Sato, 2016/11/30 23:29:39]

same

   GetStateHandler()->RemoveObserver(this, FROM_HERE);
+  observing_network_state_ = false;
 }
 
 }  // namespace arc