fix conservative rasterization for vulkan

wgpu-hal/src/vulkan/device.rs

@@ -1192,6 +1192,13 @@ impl crate::Device<super::Api> for super::Device {
         if let Some(face) = desc.primitive.cull_mode {
             vk_rasterization = vk_rasterization.cull_mode(conv::map_cull_face(face))
         }
+        let mut vk_rasterization_conservative_state =
+            vk::PipelineRasterizationConservativeStateCreateInfoEXT::builder()
+                .conservative_rasterization_mode(vk::ConservativeRasterizationModeEXT::OVERESTIMATE)
+                .build();
+        if desc.primitive.conservative {
+            vk_rasterization = vk_rasterization.push_next(&mut vk_rasterization_conservative_state);
+        }
 
         let mut vk_depth_stencil = vk::PipelineDepthStencilStateCreateInfo::builder();
         if let Some(ref ds) = desc.depth_stencil {

wgpu-types/src/lib.rs

@@ -448,7 +448,6 @@ bitflags::bitflags! {
         /// Only triangles are supported.
         ///
         /// Supported platforms:
-        /// - DX12
         /// - Vulkan
         ///
         /// This is a native only feature.

wgpu/examples/conservative-raster/main.rs

@@ -320,7 +320,7 @@ fn conservative_raster() {
         width: 1024,
         height: 768,
         optional_features: wgpu::Features::default(),
-        base_test_parameters: framework::test_common::TestParameters::default().failure(),
+        base_test_parameters: framework::test_common::TestParameters::default(),
         tollerance: 0,
         max_outliers: 0,
     });