Document that createSocketFileDescriptor throws an exception on failure.

Change-Id: Ic002b4dc8c40d798316afbab7a14bd81593e2541
diff --git a/libcore/luni/src/main/native/org_apache_harmony_luni_platform_OSNetworkSystem.cpp b/libcore/luni/src/main/native/org_apache_harmony_luni_platform_OSNetworkSystem.cpp
index c426a36..78ec2d0 100644
--- a/libcore/luni/src/main/native/org_apache_harmony_luni_platform_OSNetworkSystem.cpp
+++ b/libcore/luni/src/main/native/org_apache_harmony_luni_platform_OSNetworkSystem.cpp
@@ -1631,8 +1631,10 @@
  *
  * @param fileDescriptor the file descriptor to bind the socket to
  * @param type the socket type to create, e.g., SOCK_STREAM
+ * @throws SocketException an error occurred when creating the socket
  *
- * @return the socket file descriptor, or -1 on failure
+ * @return the socket file descriptor. On failure, an exception is thrown and
+ *         a negative value is returned.
  *
  */
 static int createSocketFileDescriptor(JNIEnv* env, jobject fileDescriptor,