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}

webrtc/rtc_tools/event_log_visualizer/plot_base.cc

@@ -12,7 +12,7 @@
 
 #include <algorithm>
 
-#include "webrtc/base/checks.h"
+#include "webrtc/rtc_base/checks.h"
 
 namespace webrtc {
 namespace plotting {