iwyu/hdr_util: Update includes.

Include what you use analysis based include update.

Change-Id: Iaa744570fe3e8f9eddc0fdbd1528c0689a3c40cb

common/hdr_util.cc

@@ -7,6 +7,11 @@
 // be found in the AUTHORS file in the root of the source tree.
 #include "hdr_util.h"
 
+#include <cstddef>
+#include <new>
+
+#include "../mkvparser.hpp"
+
 namespace libwebm {
 bool CopyPrimaryChromaticity(const mkvparser::PrimaryChromaticity& parser_pc,
                              PrimaryChromaticityPtr* muxer_pc) {

common/hdr_util.h

@@ -11,7 +11,12 @@
 #include <memory>
 
 #include "../mkvmuxer.hpp"
-#include "../mkvparser.hpp"
+
+namespace mkvparser {
+struct Colour;
+struct MasteringMetadata;
+struct PrimaryChromaticity;
+}  // namespace mkvparser
 
 namespace libwebm {