[mediacodec] Make 0 a valid encoding value.

FIDL-627 #comment

TEST: This is a blocker for a test of codecs; see FIDL-627
      for context. A test should be added to C bindings
      to prevent this issue in the future.
Change-Id: I58f2814111a6f5583a91e5818b93c26f2e693c23
diff --git a/sdk/fidl/fuchsia.sysmem/fuchsia.sysmem.api b/sdk/fidl/fuchsia.sysmem/fuchsia.sysmem.api
index 70cf796..48c76c5 100644
--- a/sdk/fidl/fuchsia.sysmem/fuchsia.sysmem.api
+++ b/sdk/fidl/fuchsia.sysmem/fuchsia.sysmem.api
@@ -6,7 +6,7 @@
   "fidl/fuchsia.sysmem/driver_connector.fidl": "d2818e5d7c2a0eae18fb006c8d802bf4",
   "fidl/fuchsia.sysmem/format_modifier.fidl": "72bd4509f27b9581544a9b3915240aac",
   "fidl/fuchsia.sysmem/formats_deprecated.fidl": "8c47d0b4664069b45b4af650e1089dde",
-  "fidl/fuchsia.sysmem/image_formats.fidl": "802774efd1813df8fc72738e0c34199c",
+  "fidl/fuchsia.sysmem/image_formats.fidl": "e3ada1fe345acead3768ccac584a9e10",
   "fidl/fuchsia.sysmem/image_formats_deprecated.fidl": "0660023fbaed2b5abca9e5038d809df8",
   "fidl/fuchsia.sysmem/usages.fidl": "64442fca34901fc3c7e45b5b640be209"
 }
\ No newline at end of file
diff --git a/zircon/system/fidl/fuchsia-sysmem/image_formats.fidl b/zircon/system/fidl/fuchsia-sysmem/image_formats.fidl
index 83414aa..51eca55 100644
--- a/zircon/system/fidl/fuchsia-sysmem/image_formats.fidl
+++ b/zircon/system/fidl/fuchsia-sysmem/image_formats.fidl
@@ -90,6 +90,8 @@
 // allocate (intentionally, to strongly discourage specifying
 // insufficiently-defined combos).
 enum ColorSpaceType {
+    // Not a valid color space type.
+    INVALID = 0;
     // sRGB
     SRGB = 1;
     // 601 NTSC ("525 line") YCbCr primaries, narrow