Modify External Texture Interface For BiPlanar Formats

Changes dawn.json entry for ExternalTexture to take a secondary plane
and adds wgpu::PredefinedColorSpace. Includes validation tests.

Bug: dawn:1082
Change-Id: I76475e4a1bce6f25c728ac0251ff582ef6369cd1
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/76282
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Brandon1 Jones <brandon1.jones@intel.com>
diff --git a/dawn.json b/dawn.json
index 40c8cf7..a0e8d2c 100644
--- a/dawn.json
+++ b/dawn.json
@@ -1314,7 +1314,8 @@
         "members": [
             {"name": "label", "type": "char", "annotation": "const*", "length": "strlen", "optional": true},
             {"name": "plane 0", "type": "texture view"},
-            {"name": "format", "type": "texture format"}
+            {"name": "plane 1", "type": "texture view", "optional": true},
+            {"name": "color space", "type": "predefined color space", "default": "srgb"}
         ]
     },
     "feature name": {
@@ -1507,6 +1508,13 @@
             {"value": 2, "name": "high performance"}
         ]
     },
+    "predefined color space": {
+        "category": "enum",
+        "values": [
+            {"value": 0, "name": "undefined"},
+            {"value": 1, "name": "srgb"}
+        ]
+    },
     "present mode": {
         "category": "enum",
         "emscripten_no_enum_table": true,