shill: Add a mockable layer for socket.h.

Mock the layer in device_info_unittest.cc. Some cleanup.

BUG=chromium-os:17394
TEST=unit tests

Change-Id: I2ddcb2fd0e01418a463596bf4e3a804b3e3023b2
Reviewed-on: http://gerrit.chromium.org/gerrit/3807
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Darin Petkov <petkov@chromium.org>
diff --git a/io_handler.h b/io_handler.h
index f6fae45..ed0f5d7 100644
--- a/io_handler.h
+++ b/io_handler.h
@@ -8,6 +8,9 @@
 namespace shill {
 
 struct InputData {
+  InputData() : buf(NULL), len(0) {}
+  InputData(unsigned char *in_buf, size_t in_len) : buf(in_buf), len(in_len) {}
+
   unsigned char *buf;
   size_t len;
 };