Create a Tether section in the system tray network list.

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

Index: ash/common/system/chromeos/network/network_list_md.cc
diff --git a/ash/common/system/chromeos/network/network_list_md.cc b/ash/common/system/chromeos/network/network_list_md.cc
index b91d6eacff82af46f21fafee6422c4b42749d584..ed1f1f2395cf9e0c2365ef356162b52d50e22423 100644
--- a/ash/common/system/chromeos/network/network_list_md.cc
+++ b/ash/common/system/chromeos/network/network_list_md.cc
@@ -182,6 +182,24 @@ class CellularHeaderRowView : public NetworkListViewMd::SectionHeaderRowView {
   DISALLOW_COPY_AND_ASSIGN(CellularHeaderRowView);
 };
 
+class TetherHeaderRowView : public NetworkListViewMd::SectionHeaderRowView {
+ public:
+  TetherHeaderRowView()
+      : SectionHeaderRowView(IDS_ASH_STATUS_TRAY_NETWORK_TETHER) {}
+
+  ~TetherHeaderRowView() override {}
+
+  const char* GetClassName() const override { return "TetherHeaderRowView"; }
+
+ protected:
+  void OnToggleToggled(bool is_on) override {
+    // TODO (hansberry): Persist toggle to settings/preferences.
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TetherHeaderRowView);
+};
+
 class WifiHeaderRowView : public NetworkListViewMd::SectionHeaderRowView {
  public:
   explicit WifiHeaderRowView(NetworkListDelegate* network_list_delegate)
@@ -263,8 +281,10 @@ NetworkListViewMd::NetworkListViewMd(NetworkListDelegate* delegate)
       no_wifi_networks_view_(nullptr),
       no_cellular_networks_view_(nullptr),
       cellular_header_view_(nullptr),
+      tether_header_view_(nullptr),
       wifi_header_view_(nullptr),
       cellular_separator_view_(nullptr),
+      tether_separator_view_(nullptr),
       wifi_separator_view_(nullptr) {
   CHECK(delegate_);
 }
@@ -376,6 +396,8 @@ void NetworkListViewMd::UpdateNetworkIcons() {
       info->type = NetworkInfo::Type::WIFI;
     else if (network->Matches(NetworkTypePattern::Cellular()))
       info->type = NetworkInfo::Type::CELLULAR;
+    else if (network->Matches(NetworkTypePattern::Tether()))
+      info->type = NetworkInfo::Type::TETHER;
     if (prohibited_by_policy) {
       info->tooltip =
           l10n_util::GetStringUTF16(IDS_ASH_STATUS_TRAY_NETWORK_PROHIBITED);
@@ -466,6 +488,24 @@ NetworkListViewMd::UpdateNetworkListEntries() {
                               new_cellular_service_paths->end());
   }
 
+  // TODO (hansberry): Use a runtime flag?
+  bool isTetherEnabled = true;

[stevenjb, 2017/02/15 20:59:04]

You will definitely want to set up a FeatureList flag for this (e.g. see
references in the code to features::kMaterialDesignSettings).

[Ryan Hansberry, 2017/02/16 22:42:20]

We already have a flag in chromeos::switches::kEnableTether, and wasn't sure if
placing another flag in chrome/common/chrome_features.h was appropriate since
this is chromeos-specific. Let me know if using
chromeos::switches::kEnableTether inside of GetTechnologyState is incorrect.

[stevenjb, 2017/02/16 22:56:35]

It looks like we already have a bunch of os specific features in there. That
said, if we already have an old school switch, using that is fine.

+  if (isTetherEnabled && pattern.MatchesPattern(NetworkTypePattern::Tether())) {
+    // TODO (hansberry): Fetch isTetherTechnologyEnabled value from
+    // settings/preferences.

[stevenjb, 2017/02/15 20:59:04]

We should leverage NetworkStateHandler::IsTechnology{Available|Enabled} for
this. i.e. allow the MT code to tell NSH when it is available / enabled, and use
the NSH interface here.

[Ryan Hansberry, 2017/02/16 22:42:20]

Was worried about the appearance of interacting with shill, but that makes more
sense. Let me know if you agree with my changes to GetTechnologyState.

[stevenjb, 2017/02/16 22:56:35]

Acknowledged.

+    bool isTetherTechnologyEnabled = true;
+    index = UpdateSectionHeaderRow(
+        NetworkTypePattern::Tether(), isTetherTechnologyEnabled, index,
+        &tether_header_view_, &tether_separator_view_);
+
+    // Add Tether networks.
+    std::unique_ptr<std::set<std::string>> new_tether_service_paths =

[stevenjb, 2017/02/15 20:59:04]

For teter these will be guids so i would name them as such (someday that will be
true for other types also).

[Ryan Hansberry, 2017/02/16 22:42:20]

Done.

+        UpdateNetworkChildren(NetworkInfo::Type::TETHER, index);
+    index += new_tether_service_paths->size();
+    new_service_paths->insert(new_tether_service_paths->begin(),
+                              new_tether_service_paths->end());
+  }
+
   if (pattern.MatchesPattern(NetworkTypePattern::WiFi())) {
     index = UpdateSectionHeaderRow(
         NetworkTypePattern::WiFi(),
@@ -575,6 +615,8 @@ int NetworkListViewMd::UpdateSectionHeaderRow(
   if (!*view) {
     if (pattern.Equals(NetworkTypePattern::Cellular()))
       *view = new CellularHeaderRowView();
+    else if (pattern.Equals(NetworkTypePattern::Tether()))
+      *view = new TetherHeaderRowView();
     else if (pattern.Equals(NetworkTypePattern::WiFi()))
       *view = new WifiHeaderRowView(delegate_);
     else