[Clean up] Introduce a BLUETOOTH_EXPORT macro to control symbol visibility outside of //device/blue…

device/bluetooth/bluetooth_socket.h

Index: device/bluetooth/bluetooth_socket.h
diff --git a/device/bluetooth/bluetooth_socket.h b/device/bluetooth/bluetooth_socket.h
index 1c7e50facb33e9ed60b4e88766c229464f723f04..8df00ff6fed69b6c039e948d1609931f48b3c057 100644
--- a/device/bluetooth/bluetooth_socket.h
+++ b/device/bluetooth/bluetooth_socket.h
@@ -9,6 +9,7 @@
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
+#include "device/bluetooth/bluetooth_export.h"
 
 namespace net {
 class IOBuffer;
@@ -27,7 +28,8 @@ class BluetoothUUID;
 // various instance methods on the same thread as the thread used at
 // construction time -- platform specific implementation are resonsible for
 // marshalling calls to a different thread if required.
-class BluetoothSocket : public base::RefCountedThreadSafe<BluetoothSocket> {
+class BLUETOOTH_EXPORT BluetoothSocket :
+    public base::RefCountedThreadSafe<BluetoothSocket> {
  public:
   enum ErrorReason { kSystemError, kIOPending, kDisconnected };