[WebGPU] Add storage-texture to GPUBindingType enum

This CL adds a "storage-texture" value to the GPUBindingType enum. Note
that this will still raise a WebGPU validation error as it is not yet
implemented in Dawn.

Bug: 877147
Change-Id: Ib3e3084063fd006b745e3e52b0249a01349e22cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1831903Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Cr-Commit-Position: refs/heads/master@{#701104}

third_party/blink/renderer/modules/webgpu/dawn_conversions.cc

@@ -32,6 +32,9 @@ DawnBindingType AsDawnEnum<DawnBindingType>(const WTF::String& webgpu_enum) {
   if (webgpu_enum == "sampled-texture") {
     return DAWN_BINDING_TYPE_SAMPLED_TEXTURE;
   }
+  if (webgpu_enum == "storage-texture") {
+    return DAWN_BINDING_TYPE_STORAGE_TEXTURE;
+  }
   NOTREACHED();
   return DAWN_BINDING_TYPE_FORCE32;
 }

third_party/blink/renderer/modules/webgpu/gpu_bind_group_layout_binding.idl

@@ -20,6 +20,7 @@ enum GPUBindingType {
     "readonly-storage-buffer",
     "sampler",
     "sampled-texture",
+    "storage-texture",
 };
 
 enum GPUTextureComponentType {