serial: Initialize Bluetooth enumerator in GetPort()

The DCHECK in serial_port_manager_impl.cc:97 is reachable if the
kEnableBluetoothSerialPortProfileInSerialApi flag is disabled or
GetDevices() is not called first and an unrecognized token is passed to
GetPort(). This change adds a check for the flag and initializes the
Bluetooth enumerator as necessary.

Bug: 1043300
Change-Id: Ib38e297f61cbc86bb9ab567084919a9e268196e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2446846
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Matt Reynolds <mattreynolds@chromium.org>
Auto-Submit: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Matt Reynolds <mattreynolds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813457}

services/device/serial/serial_port_manager_impl.cc

@@ -94,14 +94,22 @@ void SerialPortManagerImpl::GetPort(
     return;
   }
 
-  DCHECK(bluetooth_enumerator_);
-  base::Optional<std::string> address =
-      bluetooth_enumerator_->GetAddressFromToken(token);
-  if (address) {
-    ui_task_runner_->PostTask(
-        FROM_HERE, base::BindOnce(&BluetoothSerialPortImpl::Create,
-                                  bluetooth_enumerator_->GetAdapter(), *address,
-                                  std::move(receiver), std::move(watcher)));
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableBluetoothSerialPortProfileInSerialApi)) {
+    if (!bluetooth_enumerator_) {
+      bluetooth_enumerator_ =
+          std::make_unique<BluetoothSerialDeviceEnumerator>();
+      observed_enumerator_.Add(bluetooth_enumerator_.get());
+    }
+    base::Optional<std::string> address =
+        bluetooth_enumerator_->GetAddressFromToken(token);
+    if (address) {
+      ui_task_runner_->PostTask(
+          FROM_HERE,
+          base::BindOnce(&BluetoothSerialPortImpl::Create,
+                         bluetooth_enumerator_->GetAdapter(), *address,
+                         std::move(receiver), std::move(watcher)));
+    }
   }
 }
 

services/device/serial/serial_port_manager_impl_unittest.cc

@@ -225,6 +225,19 @@ TEST_F(SerialPortManagerImplTest, GetDevices) {
   loop.Run();
 }
 
+TEST_F(SerialPortManagerImplTest, GetUnknownPort) {
+  mojo::Remote<mojom::SerialPortManager> port_manager;
+  Bind(port_manager.BindNewPipeAndPassReceiver());
+
+  mojo::Remote<mojom::SerialPort> serial_port;
+  port_manager->GetPort(base::UnguessableToken::Create(),
+                        /*use_alternate_path=*/false,
+                        serial_port.BindNewPipeAndPassReceiver(),
+                        /*watcher=*/mojo::NullRemote());
+  serial_port.FlushForTesting();
+  EXPECT_FALSE(serial_port.is_connected());
+}
+
 TEST_F(SerialPortManagerImplTest, PortRemovedAndAdded) {
   SetupBluetoothEnumerator();
   mojo::Remote<mojom::SerialPortManager> port_manager;