libvpx: Pull from upstream

source/libvpx/test/md5_helper.h

Index: source/libvpx/test/md5_helper.h
diff --git a/source/libvpx/test/md5_helper.h b/source/libvpx/test/md5_helper.h
index 1db712b4e9c1b8ed208a085fe0a19f6a6ab58d91..742cf0b7b39477824e80e50fa13023b638ea959b 100644
--- a/source/libvpx/test/md5_helper.h
+++ b/source/libvpx/test/md5_helper.h
@@ -42,6 +42,10 @@ class MD5 {
     }
   }
 
+  void Add(const uint8_t *data, size_t size) {
+    MD5Update(&md5_, data, static_cast<uint32_t>(size));
+  }
+
   const char *Get(void) {
     static const char hex[16] = {
       '0', '1', '2', '3', '4', '5', '6', '7',