Generators for Emscripten

api_struct_info.json:
//* This generator is used to produce part of Emscripten's struct_info.json,
//* which is a list of struct fields that it uses to generate field offset
//* information for its own code generators.
//* https://github.com/emscripten-core/emscripten/blob/master/src/struct_info.json

library_webgpu_enum_tables.js:
//* This generator is used to produce the number-to-string mappings for
//* Emscripten's library_webgpu.js.
//* https://github.com/emscripten-core/emscripten/blob/master/src/library_webgpu.js

Change-Id: I4704509737cde4685a093eb484dd977e5a106d19
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/15240
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>

src/dawn/BUILD.gn

@@ -37,6 +37,14 @@ dawn_json_generator("dawn_headers_gen") {
   ]
 }
 
+dawn_json_generator("emscripten_bits_gen") {
+  target = "emscripten_bits"
+  outputs = [
+    "src/dawn/webgpu_struct_info.json",
+    "src/dawn/library_webgpu_enum_tables.js",
+  ]
+}
+
 source_set("dawn_headers") {
   all_dependent_configs = [ "${dawn_root}/src/common:dawn_public_include_dirs" ]
   public_deps = [