Reset Bluetooth EventHandler when it is invalid

chrome/browser/ui/bluetooth/bluetooth_chooser_controller.cc

Index: chrome/browser/ui/bluetooth/bluetooth_chooser_controller.cc
diff --git a/chrome/browser/ui/bluetooth/bluetooth_chooser_controller.cc b/chrome/browser/ui/bluetooth/bluetooth_chooser_controller.cc
index f8c98f6166bd12c38b3cb99b6e5e16635b6893e8..116596fa790eb2e382b9f63285c1c6fd48e19861 100644
--- a/chrome/browser/ui/bluetooth/bluetooth_chooser_controller.cc
+++ b/chrome/browser/ui/bluetooth/bluetooth_chooser_controller.cc
@@ -65,6 +65,8 @@ base::string16 BluetoothChooserController::GetOption(size_t index) const {
 }
 
 void BluetoothChooserController::RefreshOptions() {
+  if (event_handler_.is_null())
+    return;
   ClearAllDevices();
   event_handler_.Run(content::BluetoothChooser::Event::RESCAN, std::string());
 }
@@ -74,17 +76,23 @@ base::string16 BluetoothChooserController::GetStatus() const {
 }
 
 void BluetoothChooserController::Select(size_t index) {
+  if (event_handler_.is_null())

[Jeffrey Yasskin, 2016/08/05 20:37:51]

Would it make sense to record how often this happens to UMA? Each time it does
is probably a confusing user experience (since their selection didn't take
effect), so we'd like to fix it, and when the numbers reach 0, we can turn this
into a DCHECK.

[juncai, 2016/08/05 22:51:58]

Done.

+    return;
   DCHECK_LT(index, device_names_and_ids_.size());
   event_handler_.Run(content::BluetoothChooser::Event::SELECTED,
                      device_names_and_ids_[index].second);
 }
 
 void BluetoothChooserController::Cancel() {
+  if (event_handler_.is_null())
+    return;
   event_handler_.Run(content::BluetoothChooser::Event::CANCELLED,
                      std::string());
 }
 
 void BluetoothChooserController::Close() {
+  if (event_handler_.is_null())
+    return;
   event_handler_.Run(content::BluetoothChooser::Event::CANCELLED,
                      std::string());
 }
@@ -172,6 +180,10 @@ void BluetoothChooserController::RemoveDevice(const std::string& device_id) {
   }
 }
 
+void BluetoothChooserController::ResetEventHandler() {
+  event_handler_.Reset();
+}
+
 void BluetoothChooserController::ClearAllDevices() {
   device_names_and_ids_.clear();
   device_name_map_.clear();