Rephrase Format::aspect enum as an enum class mask

Format::aspect should be a mask so that it is easier to iterate over
and test if an aspect is present.

This CL also re-exports wgpu's EnumClassBitMask helpers in dawn_native.
It also adds an EnumMaskIterator which wraps BitSetIterator to allow
iterating over the enums in an enum mask.

Bug: dawn:439
Change-Id: I08180a45b27c6031e2f80b0fa1801716677fd813
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/24682
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jiawei Shao <jiawei.shao@intel.com>
Commit-Queue: Austin Eng <enga@chromium.org>

src/tests/BUILD.gn

@@ -156,6 +156,7 @@ test("dawn_unittests") {
     "unittests/BuddyMemoryAllocatorTests.cpp",
     "unittests/CommandAllocatorTests.cpp",
     "unittests/EnumClassBitmasksTests.cpp",
+    "unittests/EnumMaskIteratorTests.cpp",
     "unittests/ErrorTests.cpp",
     "unittests/ExtensionTests.cpp",
     "unittests/GetProcAddressTests.cpp",

src/tests/unittests/EnumMaskIteratorTests.cpp

@@ -0,0 +1,72 @@
+// Copyright 2020 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/EnumMaskIterator.h"
+
+#include "gtest/gtest.h"
+
+namespace dawn_native {
+
+    enum class TestAspect : uint8_t {
+        Color = 1,
+        Depth = 2,
+        Stencil = 4,
+    };
+
+    template <>
+    struct EnumBitmaskSize<TestAspect> {
+        static constexpr unsigned value = 3;
+    };
+
+}  // namespace dawn_native
+
+namespace wgpu {
+
+    template <>
+    struct IsDawnBitmask<dawn_native::TestAspect> {
+        static constexpr bool enable = true;
+    };
+
+}  // namespace wgpu
+
+namespace dawn_native {
+
+    static_assert(EnumBitmaskSize<TestAspect>::value == 3, "");
+
+    TEST(EnumMaskIteratorTests, None) {
+        for (TestAspect aspect : IterateEnumMask(static_cast<TestAspect>(0))) {
+            FAIL();
+            DAWN_UNUSED(aspect);
+        }
+    }
+
+    TEST(EnumMaskIteratorTests, All) {
+        TestAspect expected[] = {TestAspect::Color, TestAspect::Depth, TestAspect::Stencil};
+        uint32_t i = 0;
+        TestAspect aspects = TestAspect::Color | TestAspect::Depth | TestAspect::Stencil;
+        for (TestAspect aspect : IterateEnumMask(aspects)) {
+            EXPECT_EQ(aspect, expected[i++]);
+        }
+    }
+
+    TEST(EnumMaskIteratorTests, Partial) {
+        TestAspect expected[] = {TestAspect::Color, TestAspect::Stencil};
+        uint32_t i = 0;
+        TestAspect aspects = TestAspect::Stencil | TestAspect::Color;
+        for (TestAspect aspect : IterateEnumMask(aspects)) {
+            EXPECT_EQ(aspect, expected[i++]);
+        }
+    }
+
+}  // namespace dawn_native