Filtering bluetooth devices in the chrome os UI.

Add utility method FilterDeviceList in device/bluetooth/chromeos
to filter the devices before updating in bluetooth UI.

Extension change is in a separate CL:
https://chromium-review.googlesource.com/c/chromium/src/+/1004414/

Design doc: http://go/cros-bluetooth-filtering

Bug: 817599
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I2a5cfb2ecdacbbe633770bb0c59b2e914b4e4b1f
Reviewed-on: https://chromium-review.googlesource.com/999014
Commit-Queue: Xiaoyin Hu <xiaoyinh@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Miao-chen Chou <mcchou@chromium.org>
Reviewed-by: Rahul Chaturvedi <rkc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550046}

ash/system/bluetooth/tray_bluetooth_helper.cc

@@ -14,6 +14,7 @@
 #include "device/bluetooth/bluetooth_adapter_factory.h"
 #include "device/bluetooth/bluetooth_device.h"
 #include "device/bluetooth/bluetooth_discovery_session.h"
+#include "device/bluetooth/chromeos/bluetooth_utils.h"
 
 namespace ash {
 namespace {
@@ -75,22 +76,12 @@ void TrayBluetoothHelper::InitializeOnAdapterReady(
 
 BluetoothDeviceList TrayBluetoothHelper::GetAvailableBluetoothDevices() const {
   BluetoothDeviceList device_list;
-  device::BluetoothAdapter::DeviceList devices = adapter_->GetDevices();
-  for (device::BluetoothDevice* device : devices) {
-    if (device_list.size() == kMaximumDevicesShown)
-      break;
-
-    if (device->IsPaired() || device->IsConnecting())
-      device_list.push_back(GetBluetoothDeviceInfo(device));
-  }
-
-  for (device::BluetoothDevice* device : devices) {
-    if (device_list.size() == kMaximumDevicesShown)
-      break;
-
-    if (!device->IsPaired() && !device->IsConnecting())
-      device_list.push_back(GetBluetoothDeviceInfo(device));
-  }
+  device::BluetoothAdapter::DeviceList devices =
+      device::FilterBluetoothDeviceList(adapter_->GetDevices(),
+                                        device::BluetoothFilterType::KNOWN,
+                                        kMaximumDevicesShown);
+  for (device::BluetoothDevice* device : devices)
+    device_list.push_back(GetBluetoothDeviceInfo(device));
 
   return device_list;
 }

device/bluetooth/BUILD.gn

@@ -395,6 +395,12 @@ component("bluetooth") {
           "dbus/dbus_thread_manager_linux.h",
         ]
       }
+      if (is_chromeos) {
+        sources += [
+          "chromeos/bluetooth_utils.cc",
+          "chromeos/bluetooth_utils.h",
+        ]
+      }
       deps += [ "//dbus" ]
     } else {  # !use_dbus
       if (is_chromecast && is_linux) {

device/bluetooth/chromeos/bluetooth_utils.cc

@@ -0,0 +1,63 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "device/bluetooth/chromeos/bluetooth_utils.h"
+
+namespace device {
+
+namespace {
+
+// Get limited number of devices from |devices| and
+// prioritize paired/connecting devices over other devices.
+BluetoothAdapter::DeviceList GetLimitedNumDevices(
+    size_t max_device_num,
+    const BluetoothAdapter::DeviceList& devices) {
+  // If |max_device_num| is 0, it means there's no limit.
+  if (max_device_num == 0)
+    return devices;
+
+  BluetoothAdapter::DeviceList result;
+  for (BluetoothDevice* device : devices) {
+    if (result.size() == max_device_num)
+      break;
+
+    if (device->IsPaired() || device->IsConnecting())
+      result.push_back(device);
+  }
+
+  for (BluetoothDevice* device : devices) {
+    if (result.size() == max_device_num)
+      break;
+
+    if (!device->IsPaired() && !device->IsConnecting())
+      result.push_back(device);
+  }
+
+  return result;
+}
+
+// Filter out unknown devices from the list.
+BluetoothAdapter::DeviceList FilterUnknownDevices(
+    const BluetoothAdapter::DeviceList& devices) {
+  BluetoothAdapter::DeviceList result;
+  for (BluetoothDevice* device : devices) {
+    if (device->GetDeviceType() != device::BluetoothDeviceType::UNKNOWN)
+      result.push_back(device);
+  }
+  return result;
+}
+
+}  // namespace
+
+device::BluetoothAdapter::DeviceList FilterBluetoothDeviceList(
+    const BluetoothAdapter::DeviceList& devices,
+    BluetoothFilterType filter_type,
+    int max_devices) {
+  BluetoothAdapter::DeviceList filtered_devices =
+      filter_type == BluetoothFilterType::KNOWN ? FilterUnknownDevices(devices)
+                                                : devices;
+  return GetLimitedNumDevices(max_devices, filtered_devices);
+}
+
+}  // namespace device

device/bluetooth/chromeos/bluetooth_utils.h

@@ -0,0 +1,31 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef DEVICE_BLUETOOTH_CHROMEOS_BLUETOOTH_UTILS_H_
+#define DEVICE_BLUETOOTH_CHROMEOS_BLUETOOTH_UTILS_H_
+
+#include "device/bluetooth/bluetooth_adapter.h"
+#include "device/bluetooth/bluetooth_export.h"
+
+// This file contains common utilities for filtering the bluetooth devices
+// based on the filter criteria.
+namespace device {
+
+enum class BluetoothFilterType {
+  // No filtering, all bluetooth devices will be returned.
+  ALL = 0,
+  // Return bluetooth devices that are known to the UI.
+  // I.e. bluetooth device type != UNKNOWN
+  KNOWN,
+};
+
+// Return filtered devices based on the filter type and max number of devices.
+device::BluetoothAdapter::DeviceList DEVICE_BLUETOOTH_EXPORT
+FilterBluetoothDeviceList(const BluetoothAdapter::DeviceList& devices,
+                          BluetoothFilterType filter_type,
+                          int max_devices);
+
+}  // namespace device
+
+#endif  // DEVICE_BLUETOOTH_CHROMEOS_BLUETOOTH_UTILS_H_