Complete the sampler object to match WebGPU

WebGPUSampler is much more complete than Dawn's Sampler.
This patch implement the missing part.

BUG=dawn:47

Change-Id: Ief45cb9710493e9d79ddab60fe3be5a123b76ebd
Reviewed-on: https://dawn-review.googlesource.com/c/3540
Commit-Queue: Shaobo Yan <shaobo.yan@intel.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/dawn_native/vulkan/UtilsVulkan.cpp b/src/dawn_native/vulkan/UtilsVulkan.cpp
new file mode 100644
index 0000000..723a6bb
--- /dev/null
+++ b/src/dawn_native/vulkan/UtilsVulkan.cpp
@@ -0,0 +1,44 @@
+// Copyright 2019 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "dawn_native/vulkan/UtilsVulkan.h"
+
+#include "common/Assert.h"
+
+namespace dawn_native { namespace vulkan {
+
+    VkCompareOp ToVulkanCompareOp(dawn::CompareFunction op) {
+        switch (op) {
+            case dawn::CompareFunction::Always:
+                return VK_COMPARE_OP_ALWAYS;
+            case dawn::CompareFunction::Equal:
+                return VK_COMPARE_OP_EQUAL;
+            case dawn::CompareFunction::Greater:
+                return VK_COMPARE_OP_GREATER;
+            case dawn::CompareFunction::GreaterEqual:
+                return VK_COMPARE_OP_GREATER_OR_EQUAL;
+            case dawn::CompareFunction::Less:
+                return VK_COMPARE_OP_LESS;
+            case dawn::CompareFunction::LessEqual:
+                return VK_COMPARE_OP_LESS_OR_EQUAL;
+            case dawn::CompareFunction::Never:
+                return VK_COMPARE_OP_NEVER;
+            case dawn::CompareFunction::NotEqual:
+                return VK_COMPARE_OP_NOT_EQUAL;
+            default:
+                UNREACHABLE();
+        }
+    }
+
+}}  // namespace dawn_native::vulkan