Fix -Wreturn-stack-address in ble_scanner_impl_unittest.cc

  ../../chromeos/services/secure_channel/ble_scanner_impl_unittest.cc:231:12:
  error: address of stack memory associated with local variable
  'fake_bluetooth_device' returned [-Werror,-Wreturn-stack-address]
      return fake_bluetooth_device.get();
             ^~~~~~~~~~~~~~~~~~~~~

I guess the test worked before because it didn't actually dereference the
pointer.

Bug: 992458
Change-Id: I82f189588644a63de1a9f16dbf158dfcdca5e5a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1751789Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686465}

chromeos/services/secure_channel/ble_scanner_impl_unittest.cc

@@ -160,12 +160,12 @@ class SecureChannelBleScannerImplTest : public testing::Test {
         service_data, expected_remote_device, is_background_advertisement);
 
     size_t num_results_before_call = results.size();
-    FakeBluetoothDevice* fake_bluetooth_device =
+    std::unique_ptr<FakeBluetoothDevice> fake_bluetooth_device =
         SimulateScanResult(service_data);
     EXPECT_EQ(num_results_before_call + 1u, results.size());
 
     EXPECT_EQ(expected_remote_device, std::get<0>(results.back()));
-    EXPECT_EQ(fake_bluetooth_device, std::get<1>(results.back()));
+    EXPECT_EQ(fake_bluetooth_device.get(), std::get<1>(results.back()));
     EXPECT_EQ(is_background_advertisement ? ConnectionRole::kListenerRole
                                           : ConnectionRole::kInitiatorRole,
               std::get<2>(results.back()));
@@ -209,7 +209,8 @@ class SecureChannelBleScannerImplTest : public testing::Test {
   }
 
  private:
-  FakeBluetoothDevice* SimulateScanResult(const std::string& service_data) {
+  std::unique_ptr<FakeBluetoothDevice> SimulateScanResult(
+      const std::string& service_data) {
     static const int16_t kFakeRssi = -70;
     static const std::vector<uint8_t> kFakeEir;
 
@@ -228,7 +229,7 @@ class SecureChannelBleScannerImplTest : public testing::Test {
                                            kFakeRssi, kFakeEir);
     }
 
-    return fake_bluetooth_device.get();
+    return fake_bluetooth_device;
   }
 
   const multidevice::RemoteDeviceRefList test_devices_;