Fix symbol visibility of StreamingListener.

googletest/src/gtest-internal-inl.h

@@ -1032,7 +1032,7 @@ class TestResultAccessor {
 #if GTEST_CAN_STREAM_RESULTS_
 
 // Streams test results to the given port on the given host machine.
-class StreamingListener : public EmptyTestEventListener {
+class GTEST_API_ StreamingListener : public EmptyTestEventListener {
  public:
   // Abstract base class for writing strings to a socket.
   class AbstractSocketWriter {