Fix MSAN compile error

Change-Id: I2ac07f2da5e08a3dbefc59fb860d69817906df41
Reviewed-on: https://skia-review.googlesource.com/49441
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>

tools/timer/Timer.cpp

@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 #include "Timer.h"
+#include <stdio.h>
 
 SkString HumanizeMs(double ms) {
     if (ms > 60e+3)  return SkStringPrintf("%.3gm", ms/60e+3);