Clean up a few IWYU issues

Spun off from the SkTFitsIn CL.

Change-Id: I686d680df6a36ebc02db3847ad5e2cedcbcd67ef
Reviewed-on: https://skia-review.googlesource.com/134083
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/include/private/SkPathRef.h b/include/private/SkPathRef.h
index 9ce1aee..d9c8849 100644
--- a/include/private/SkPathRef.h
+++ b/include/private/SkPathRef.h
@@ -17,6 +17,7 @@
 #include "SkRect.h"
 #include "SkRefCnt.h"
 #include "SkTemplates.h"
+#include <limits>
 
 class SkRBuffer;
 class SkWBuffer;