[rtp_rtcp] lint build/include errors fixed

webrtc/modules/rtp_rtcp/source/ssrc_database.cc

Index: webrtc/modules/rtp_rtcp/source/ssrc_database.cc
diff --git a/webrtc/modules/rtp_rtcp/source/ssrc_database.cc b/webrtc/modules/rtp_rtcp/source/ssrc_database.cc
index 6fb7c4701a39daf168ea16e78033ebce61395093..45c9c8070c25cab372c1d84a9e912d3feef95a84 100644
--- a/webrtc/modules/rtp_rtcp/source/ssrc_database.cc
+++ b/webrtc/modules/rtp_rtcp/source/ssrc_database.cc
@@ -13,11 +13,13 @@
 #include <assert.h>
 #include <stdlib.h>
 
+#include <string>
+
 #include "webrtc/system_wrappers/include/critical_section_wrapper.h"
 
 #ifdef _WIN32
-    #include <windows.h>
     #include <MMSystem.h> //timeGetTime
+    #include <windows.h>
 
 // TODO(hellner): investigate if it is necessary to disable these warnings.
     #pragma warning(disable:4311)
@@ -25,8 +27,8 @@
 #else
     #include <stdio.h>
     #include <string.h>
-    #include <time.h>
     #include <sys/time.h>
+    #include <time.h>
 #endif
 
 namespace webrtc {