H264SPS: Centralize computation of coded size and visible rect.

media/filters/h264_parser.h

Index: media/filters/h264_parser.h
diff --git a/media/filters/h264_parser.h b/media/filters/h264_parser.h
index c557383022023dbfacab93e9cc076cf6aab3bd14..64519e8fd7a95eed0bd4fa2f00ddb36c7735c70f 100644
--- a/media/filters/h264_parser.h
+++ b/media/filters/h264_parser.h
@@ -15,11 +15,17 @@
 #include <vector>
 
 #include "base/macros.h"
+#include "base/optional.h"
 #include "media/base/media_export.h"
 #include "media/base/ranges.h"
 #include "media/base/video_codecs.h"
 #include "media/filters/h264_bit_reader.h"
 
+namespace gfx {
+class Rect;
+class Size;
+}
+
 namespace media {
 
 struct SubsampleEntry;
@@ -166,6 +172,12 @@ struct MEDIA_EXPORT H264SPS {
   bool low_delay_hrd_flag;
 
   int chroma_array_type;
+
+  // Helpers to compute frequently-used values. These methods return
+  // base::nullopt if they encounter integer overflow. They do not verify that
+  // the results are in-spec for the given profile or level.
+  base::Optional<gfx::Size> GetCodedSize() const;
+  base::Optional<gfx::Rect> GetVisibleRect() const;
 };
 
 struct MEDIA_EXPORT H264PPS {