[emscripten] Add WGPURequestAdapterOptions featureLevel option

Spec PR: https://github.com/webgpu-native/webgpu-headers/pull/399

Bug: 366151404
Change-Id: I4be2afaaf4a92fbf0df0172e1a00f7db212f720f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/220894
Reviewed-by: Loko Kung <lokokung@google.com>
Commit-Queue: Fr <beaufort.francois@gmail.com>
diff --git a/third_party/emdawnwebgpu/library_webgpu.js b/third_party/emdawnwebgpu/library_webgpu.js
index a766731..4629d2f 100644
--- a/third_party/emdawnwebgpu/library_webgpu.js
+++ b/third_party/emdawnwebgpu/library_webgpu.js
@@ -1909,7 +1909,9 @@
     var opts;
     if (options) {
       {{{ gpu.makeCheckDescriptor('options') }}}
+      var featureLevel = {{{ gpu.makeGetU32('options', C_STRUCTS.WGPURequestAdapterOptions.featureLevel) }}};
       opts = {
+        "featureLevel": featureLevel === {{ gpu.FeatureLevel.Compatibility }} ? "compatibility" : "core",
         "powerPreference": WebGPU.PowerPreference[
           {{{ gpu.makeGetU32('options', C_STRUCTS.WGPURequestAdapterOptions.powerPreference) }}}],
         "forceFallbackAdapter":