Introduce a client minimum picture pool size

ppapi/proxy/video_decoder_constants.h

Index: ppapi/proxy/video_decoder_constants.h
diff --git a/ppapi/proxy/video_decoder_constants.h b/ppapi/proxy/video_decoder_constants.h
index 666ad46044dd6970b36207b761016ec64085bbe5..08ea9c743b3955415efb4a3bb58aa265c4d2273d 100644
--- a/ppapi/proxy/video_decoder_constants.h
+++ b/ppapi/proxy/video_decoder_constants.h
@@ -19,7 +19,12 @@ enum {
 
   // Maximum size of shared-memory buffers (4 MB). This should be enough even
   // for 4K video at reasonable compression levels.
-  kMaximumBitstreamBufferSize = 4 << 20
+  kMaximumBitstreamBufferSize = 4 << 20,
+
+  // The maximum number of pictures that the client can pass in for
+  // min_picture_count, just as a sanity check on the argument.
+  // This should match the constant of the same name in test_video_decoder.cc.
+  kMaximumPictureCount = 100
 };
 
 }  // namespace proxy