Rename "extension" to "feature"

This CL renames "extension" to "feature" to follow WebGPU. It still
supports both. A future Chromium CL will pick this change, then all
"extension" occurrences will be removed.

Change-Id: I070e32d7ae042f9b846df01f200b39f6741a0a14
Bug: dawn:1149
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/65664
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>

src/dawn_native/Features.h

@@ -0,0 +1,74 @@
+// 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.
+
+#ifndef DAWNNATIVE_FEATURES_H_
+#define DAWNNATIVE_FEATURES_H_
+
+#include <bitset>
+#include <unordered_map>
+#include <vector>
+
+#include "dawn_native/DawnNative.h"
+
+namespace dawn_native {
+
+    enum class Feature {
+        TextureCompressionBC,
+        TextureCompressionETC2,
+        TextureCompressionASTC,
+        ShaderFloat16,
+        PipelineStatisticsQuery,
+        TimestampQuery,
+        DepthClamping,
+
+        // Dawn-specific
+        DawnInternalUsages,
+        MultiPlanarFormats,
+
+        EnumCount,
+        InvalidEnum = EnumCount,
+        FeatureMin = TextureCompressionBC,
+    };
+
+    // A wrapper of the bitset to store if an feature is enabled or not. This wrapper provides the
+    // convenience to convert the enums of enum class Feature to the indices of a bitset.
+    struct FeaturesSet {
+        std::bitset<static_cast<size_t>(Feature::EnumCount)> featuresBitSet;
+
+        void EnableFeature(Feature feature);
+        bool IsEnabled(Feature feature) const;
+        std::vector<const char*> GetEnabledFeatureNames() const;
+        void InitializeDeviceProperties(WGPUDeviceProperties* properties) const;
+    };
+
+    const char* FeatureEnumToName(Feature feature);
+
+    class FeaturesInfo {
+      public:
+        FeaturesInfo();
+
+        // Used to query the details of an feature. Return nullptr if featureName is not a valid
+        // name of an feature supported in Dawn
+        const FeatureInfo* GetFeatureInfo(const char* featureName) const;
+        Feature FeatureNameToEnum(const char* featureName) const;
+        FeaturesSet FeatureNamesToFeaturesSet(
+            const std::vector<const char*>& requiredFeatures) const;
+
+      private:
+        std::unordered_map<std::string, Feature> mFeatureNameToEnumMap;
+    };
+
+}  // namespace dawn_native
+
+#endif  // DAWNNATIVE_FEATURES_H_