Update includes for webrtc/{base => rtc_base} rename (2/3)

I used a command like this to update the paths:
perl -pi -e "s/webrtc\/base/webrtc\/rtc_base/g" `find webrtc/rtc_base -name "*.cc" -o -name "*.h"`

BUG=webrtc:7634
NOPRESUBMIT=True # cpplint errors that aren't caused by this CL.

Review-Url: https://codereview.webrtc.org/2969623003
Cr-Commit-Position: refs/heads/master@{#18870}
diff --git a/webrtc/system_wrappers/source/trace_impl.cc b/webrtc/system_wrappers/source/trace_impl.cc
index 30a8816..513327e 100644
--- a/webrtc/system_wrappers/source/trace_impl.cc
+++ b/webrtc/system_wrappers/source/trace_impl.cc
@@ -15,8 +15,8 @@
 #include <stdio.h>
 #include <string.h>
 
-#include "webrtc/base/atomicops.h"
-#include "webrtc/base/platform_thread.h"
+#include "webrtc/rtc_base/atomicops.h"
+#include "webrtc/rtc_base/platform_thread.h"
 #ifdef _WIN32
 #include "webrtc/system_wrappers/source/trace_win.h"
 #else