Collect number of paired BT devices.

Bug: 31602591 
Change-Id: I61adee8b20d57e2a1e284ed21a46d1766f059d4a
diff --git a/src/com/android/bluetooth/btservice/AdapterService.java b/src/com/android/bluetooth/btservice/AdapterService.java
index 72f4ffa..2e868eb 100644
--- a/src/com/android/bluetooth/btservice/AdapterService.java
+++ b/src/com/android/bluetooth/btservice/AdapterService.java
@@ -2481,6 +2481,7 @@
 
     private void dumpJava(FileDescriptor fd) {
         BluetoothProto.BluetoothLog log = new BluetoothProto.BluetoothLog();
+        log.setNumBondedDevices(getBondedDevices().length);
 
         for (ProfileService profile : mProfiles) {
             profile.dumpProto(log);
diff --git a/src/com/android/bluetooth/btservice/bluetooth.proto b/src/com/android/bluetooth/btservice/bluetooth.proto
index 11311ea..77ded78 100644
--- a/src/com/android/bluetooth/btservice/bluetooth.proto
+++ b/src/com/android/bluetooth/btservice/bluetooth.proto
@@ -25,6 +25,9 @@
 
   // Scan event information.
   repeated ScanEvent scan_event = 4;
+
+  // Number of bonded devices.
+  optional int32 num_bonded_devices = 5;
 }
 
 // The information about the device.