Implement RenderBundle in the frontend

This CL implements RenderBundle and RenderBundleEncoder in the frontend
and adds unittests for validation.

Bug: dawn:154
Change-Id: Ice5ecd384cd627ad270b73052408f8139d1ea5f4
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/9221
Commit-Queue: Austin Eng <enga@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>

src/utils/ComboRenderBundleEncoderDescriptor.cpp

@@ -0,0 +1,30 @@
+// 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 "utils/ComboRenderBundleEncoderDescriptor.h"
+
+#include "utils/DawnHelpers.h"
+
+namespace utils {
+
+    ComboRenderBundleEncoderDescriptor::ComboRenderBundleEncoderDescriptor() {
+        dawn::RenderBundleEncoderDescriptor* descriptor = this;
+
+        descriptor->sampleCount = 1;
+        descriptor->depthStencilFormat = nullptr;
+        descriptor->colorFormatsCount = 0;
+        descriptor->colorFormats = &cColorFormats[0];
+    }
+
+}  // namespace utils