Add missing includes to simple_encode.h

Change-Id: Ic3bb2450443c52ba3df1ed6729cecdab51245e76
diff --git a/vp9/simple_encode.h b/vp9/simple_encode.h
index 6033d93..5d6972e 100644
--- a/vp9/simple_encode.h
+++ b/vp9/simple_encode.h
@@ -11,6 +11,8 @@
 #ifndef VPX_VP9_SIMPLE_ENCODE_H_
 #define VPX_VP9_SIMPLE_ENCODE_H_
 
+#include <cstddef>
+#include <cstdint>
 #include <cstdio>
 #include <memory>
 #include <vector>
@@ -76,6 +78,7 @@
 
  private:
   class EncodeImpl;
+
   int frame_width_;
   int frame_height_;
   int frame_rate_num_;