Keep focused device in Bluetooth device list when the list is refreshed.

ash/common/system/chromeos/bluetooth/tray_bluetooth.cc

Index: ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
diff --git a/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc b/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
index 3eeae17a49fd3062f89367f67ad6fd43e95daebd..08adff62477101a4c49788bc53f443fee6fdb0cc 100644
--- a/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
+++ b/ash/common/system/chromeos/bluetooth/tray_bluetooth.cc
@@ -269,6 +269,8 @@ class BluetoothDetailedView : public TrayDetailsView {
   }
 
   void UpdateDeviceScrollList() {
+    std::string focused_device_address = GetFocusedDeviceAddress();
+
     device_map_.clear();
     scroll_content()->RemoveAllChildViews(true);
 
@@ -318,6 +320,10 @@ class BluetoothDetailedView : public TrayDetailsView {
       }
     }
 
+    // Focus the device which was focused before the device-list update.
+    if (!focused_device_address.empty())
+      FocusDeviceByAddress(focused_device_address);

[fukino, 2017/03/16 14:20:15]

Here, I restore the focus based on the device address rather than index in the
list.
I believe this is better considering the case when the list is long and the
number of upper items from the focused item changes.
However, when the focused item disappears from the list, the focus will be
reset. I assume it is a rare case, but WDYT?

[tdanderson, 2017/03/16 20:40:14]

Sounds good to me, I think focusing based on address is the right way to do it.
And if the focused element disappears, then I think resetting focus is perfectly
reasonable.

+
     scroll_content()->InvalidateLayout();
   }
 
@@ -548,6 +554,23 @@ class BluetoothDetailedView : public TrayDetailsView {
     return container;
   }
 
+  std::string GetFocusedDeviceAddress() {
+    for (auto& view_and_address : device_map_) {
+      if (view_and_address.first->HasFocus())
+        return view_and_address.second;
+    }
+    return std::string();
+  }
+
+  void FocusDeviceByAddress(const std::string& address) {
+    for (auto& view_and_address : device_map_) {
+      if (view_and_address.second == address) {
+        view_and_address.first->RequestFocus();
+        return;
+      }
+    }
+  }
+
   LoginStatus login_;
 
   std::map<views::View*, std::string> device_map_;