[Nearby] Allow BluetoothSocket::Close() to be called multiple times

After a successful payload transfer, BluetoothSocket::Close() will be
called multiple times (see crbug/1142071). In this CL, we check if the
underlying socket has already been disconnected and reset before trying
to disconnect and reset. Without this check, the Nearby process will
crash after a successful share.

Verified by manually testing Chromebook-->Android transfers.

Fixed: 1142071
Change-Id: I1b2fd0a092f1025f95c2eed5253862805e46b034
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2500982
Commit-Queue: Josh Nohle <nohle@chromium.org>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Auto-Submit: Josh Nohle <nohle@chromium.org>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821033}

chrome/services/sharing/nearby/platform/bluetooth_socket.cc

@@ -314,8 +314,7 @@ BluetoothSocket::BluetoothSocket(
 }
 
 BluetoothSocket::~BluetoothSocket() {
-  if (socket_)
-    Close();
+  Close();
 
   // These properties must be destroyed on the same sequence they are later run
   // on. See |task_runner_|.
@@ -347,8 +346,10 @@ OutputStream& BluetoothSocket::GetOutputStream() {
 }
 
 Exception BluetoothSocket::Close() {
-  socket_->Disconnect();
-  socket_.reset();
+  if (socket_) {
+    socket_->Disconnect();
+    socket_.reset();
+  }
   Exception input_exception = input_stream_->Close();
   Exception output_exception = output_stream_->Close();
   if (input_exception.Ok() && output_exception.Ok())

chrome/services/sharing/nearby/platform/bluetooth_socket_unittest.cc

@@ -178,6 +178,10 @@ TEST_F(BluetoothSocketTest, TestClose) {
   fake_socket_->SetOnDestroyCallback(run_loop.QuitClosure());
   EXPECT_TRUE(bluetooth_socket_->Close().Ok());
   run_loop.Run();
+
+  // Ensure that calls to Close() succeed even after the underlying socket is
+  // destroyed.
+  EXPECT_TRUE(bluetooth_socket_->Close().Ok());
 }
 
 TEST_F(BluetoothSocketTest, TestDestroy) {