Increase Web Bluetooth device scanning duration

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 f658f69fe277d266ea952c9ce1091d047698ca27..5333142525a9b496b071d4137c02b4956ca01736 100644
--- a/chrome/browser/ui/bluetooth/bluetooth_chooser_controller.cc
+++ b/chrome/browser/ui/bluetooth/bluetooth_chooser_controller.cc
@@ -32,6 +32,11 @@ void RecordInteractionWithChooser(bool has_null_handler) {
   UMA_HISTOGRAM_BOOLEAN("Bluetooth.Web.ChooserInteraction", has_null_handler);
 }
 
+void RecordScanningDuration(const base::TimeDelta& duration) {
+  UMA_HISTOGRAM_MEDIUM_TIMES("Bluetooth.Web.RequestDevice.ScanningDuration",

[scheib, 2016/11/17 05:19:59]

"UMA_HISTOGRAM_LONG_TIMES" instead I think. We've discussed possibly going
longer than 3 minutes that MEDIUM provides, and we should future proof this UMA.
Looking at bucket distribution, the LONG variant still offers useful resolution
of ~20 second sized buckets around the 1 minute value.

[juncai, 2016/11/17 21:15:30]

Done.

+                             duration);
+}
+
 }  // namespace
 
 BluetoothChooserController::BluetoothChooserController(
@@ -169,6 +174,7 @@ void BluetoothChooserController::OnDiscoveryStateChanged(
     content::BluetoothChooser::DiscoveryState state) {
   switch (state) {
     case content::BluetoothChooser::DiscoveryState::DISCOVERING:
+      scanning_start_time_ = base::TimeTicks::Now();
       status_text_ =
           l10n_util::GetStringUTF16(IDS_BLUETOOTH_DEVICE_CHOOSER_SCANNING);
       if (view()) {
@@ -195,6 +201,11 @@ void BluetoothChooserController::AddOrUpdateDevice(
     bool is_gatt_connected,
     bool is_paired,
     int signal_strength_level) {
+  if (scanning_start_time_) {

[scheib, 2016/11/17 05:19:59]

Why is the scanning start time reset when a new device is discovered? I think we
should record the time scanning was active for, that is, when the dialog is
closed or scanning times out. Perhaps bluetooth_device_chooser_controller.cc is
a better place to track this UMA?

[juncai, 2016/11/17 21:15:30]

Done.

+    RecordScanningDuration(base::TimeTicks::Now() -
+                           scanning_start_time_.value());
+    scanning_start_time_.reset();
+  }
   auto name_it = device_id_to_name_map_.find(device_id);
   if (name_it != device_id_to_name_map_.end()) {
     if (should_update_name) {