Fix doxygen warnings

Change-Id: I5b3765ca0362e517990334d47f9defa673732a04
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/55800
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/reader/spirv/entry_point_info.h

@@ -26,8 +26,11 @@ namespace spirv {
 
 /// The size of an integer-coordinate grid, in the x, y, and z dimensions.
 struct GridSize {
+  /// x value
   uint32_t x = 0;
+  /// y value
   uint32_t y = 0;
+  /// z value
   uint32_t z = 0;
 };
 

src/reader/spirv/parser_impl.h

@@ -99,13 +99,13 @@ struct WorkgroupSizeInfo {
   uint32_t component_type_id = 0u;
   /// The SPIR-V IDs of the X, Y, and Z components of the workgroup size
   /// builtin.
-  uint32_t x_id = 0u;
-  uint32_t y_id = 0u;
-  uint32_t z_id = 0u;
+  uint32_t x_id = 0u;  /// X component ID
+  uint32_t y_id = 0u;  /// Y component ID
+  uint32_t z_id = 0u;  /// Z component ID
   /// The effective workgroup size, if this is a compute shader.
-  uint32_t x_value = 0u;
-  uint32_t y_value = 0u;
-  uint32_t z_value = 0u;
+  uint32_t x_value = 0u;  /// X workgroup size
+  uint32_t y_value = 0u;  /// Y workgroup size
+  uint32_t z_value = 0u;  /// Z workgroup size
 };
 
 /// Parser implementation for SPIR-V.
@@ -325,6 +325,7 @@ class ParserImpl : Reader {
   /// @returns true if parser is still successful.
   bool RegisterWorkgroupSizeBuiltin();
 
+  /// @returns the workgroup size builtin
   const WorkgroupSizeInfo& workgroup_size_builtin() {
     return workgroup_size_builtin_;
   }

src/transform/zero_init_workgroup_memory.cc

@@ -26,7 +26,7 @@
 namespace tint {
 namespace transform {
 
-// PIMPL state for the ZeroInitWorkgroupMemory transform
+/// PIMPL state for the ZeroInitWorkgroupMemory transform
 struct ZeroInitWorkgroupMemory::State {
   /// The clone context
   CloneContext& ctx;