[topaz][sdk] add composition_delegate to SDK

Bug: DX-1089  #comment
Change-Id: If3e29b39d0fea001a94a5e8aab43c076657c3efc
diff --git a/public/sdk/BUILD.gn b/public/sdk/BUILD.gn
index a1b6701..d7a3f90 100644
--- a/public/sdk/BUILD.gn
+++ b/public/sdk/BUILD.gn
@@ -20,6 +20,7 @@
 
   deps = [
     "//topaz/bin/fidlgen_dart:fidlgen_dart_sdk($host_toolchain)",
+    "//topaz/public/dart/composition_delegate:composition_delegate_sdk($dart_toolchain)",
     "//topaz/public/dart/fidl:fidl_sdk($dart_toolchain)",
     "//topaz/public/dart/fuchsia:fuchsia_sdk($dart_toolchain)",
     "//topaz/public/dart/fuchsia_logger:fuchsia_logger_sdk($dart_toolchain)",
diff --git a/public/sdk/fuchsia_dart.api b/public/sdk/fuchsia_dart.api
index a720de1..539b956 100644
--- a/public/sdk/fuchsia_dart.api
+++ b/public/sdk/fuchsia_dart.api
@@ -1,3 +1,4 @@
+sdk://dart/composition_delegate
 sdk://dart/fidl
 sdk://dart/fuchsia
 sdk://dart/fuchsia_logger