gpu: add ExternalTexture.BindingEntry

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

gpu/TODO-webgpu.h

@@ -1,8 +1,3 @@
-typedef struct WGPUExternalTextureBindingEntry {
-    WGPUChainedStruct chain;
-    WGPUExternalTexture externalTexture;
-} WGPUExternalTextureBindingEntry;
-
 typedef struct WGPUExternalTextureBindingLayout {
     WGPUChainedStruct chain;
 } WGPUExternalTextureBindingLayout;

gpu/src/dawn.zig

@@ -14,20 +14,17 @@ pub const EncoderInternalUsageDescriptor = struct {
 };
 
 pub const InstanceDescriptor = extern struct {
-    // TODO: file an issue on Dawn: why not named nextInChain?
     chain: ChainedStruct,
     additional_runtime_search_paths_count: u32,
     additional_runtime_search_paths: [*]const u8,
 };
 
 pub const TextureInternalUsageDescriptor = extern struct {
-    // TODO: file an issue on Dawn: why not named nextInChain?
     chain: ChainedStruct,
     internal_usage: Texture.UsageFlags,
 };
 
 pub const TogglesDeviceDescriptor = extern struct {
-    // TODO: file an issue on Dawn: why not named nextInChain?
     chain: ChainedStruct,
     force_enabled_toggles_count: u32,
     force_enabled_toggles: [*]const u8,

gpu/src/external_texture.zig

@@ -1,6 +1,13 @@
+pub const ChainedStruct = @import("types.zig").ChainedStruct;
+
 pub const ExternalTexture = enum(usize) {
     _,
 
     // TODO: verify there is a use case for nullable value of this type.
     pub const none: ExternalTexture = @intToEnum(ExternalTexture, 0);
+
+    pub const BindingEntry = extern struct {
+        chain: ChainedStruct,
+        external_texture: ExternalTexture,
+    };
 };