[ash-md] Disables proxy settings button when there are no networks

ash/common/system/chromeos/network/network_state_list_detailed_view.cc

Index: ash/common/system/chromeos/network/network_state_list_detailed_view.cc
diff --git a/ash/common/system/chromeos/network/network_state_list_detailed_view.cc b/ash/common/system/chromeos/network/network_state_list_detailed_view.cc
index 3a5ce73eb6d51793b15ab0a0712134daca5daf5e..9e2e72e28586b678b17c142efe52fc76968fef07 100644
--- a/ash/common/system/chromeos/network/network_state_list_detailed_view.cc
+++ b/ash/common/system/chromeos/network/network_state_list_detailed_view.cc
@@ -348,6 +348,7 @@ NetworkStateListDetailedView::~NetworkStateListDetailedView() {
 
 void NetworkStateListDetailedView::Update() {
   UpdateNetworkList();
+  UpdateHeaderButtons();
   Layout();
 }
 
@@ -528,6 +529,14 @@ void NetworkStateListDetailedView::UpdateNetworkList() {
   network_list_view_->Update();
 }
 
+void NetworkStateListDetailedView::UpdateHeaderButtons() {
+  if (proxy_settings_button_md_) {
+    proxy_settings_button_md_->SetEnabled(
+        NetworkHandler::Get()->network_state_handler()->DefaultNetwork() !=
+        nullptr);
+  }
+}
+
 bool NetworkStateListDetailedView::OrderChild(views::View* view, int index) {
   if (scroll_content()->child_at(index) != view) {
     scroll_content()->ReorderChildView(view, index);