null backend: fix resource usage after cmdbuf transition (#63)

and test it.

src/tests/CMakeLists.txt

@@ -36,6 +36,7 @@ add_executable(nxt_unittests
     ${VALIDATION_TESTS_DIR}/FramebufferValidationTests.cpp
     ${VALIDATION_TESTS_DIR}/InputStateValidationTests.cpp
     ${VALIDATION_TESTS_DIR}/RenderPassValidationTests.cpp
+    ${VALIDATION_TESTS_DIR}/UsageValidationTests.cpp
     ${VALIDATION_TESTS_DIR}/ValidationTest.cpp
     ${VALIDATION_TESTS_DIR}/ValidationTest.h
     ${TESTS_DIR}/UnittestsMain.cpp

src/tests/unittests/validation/UsageValidationTests.cpp

@@ -0,0 +1,56 @@
+// Copyright 2017 The NXT 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 "tests/unittests/validation/ValidationTest.h"
+
+#include <gmock/gmock.h>
+
+using namespace testing;
+
+class UsageValidationTest : public ValidationTest {
+    protected:
+        nxt::Queue queue;
+
+    private:
+        void SetUp() override {
+            ValidationTest::SetUp();
+            queue = device.CreateQueueBuilder().GetResult();
+        }
+};
+
+// Test that command buffer submit changes buffer usage
+TEST_F(UsageValidationTest, UsageAfterCommandBuffer) {
+    // TODO(kainino@chromium.org): This needs to be tested on every backend.
+    // Should we make an end2end test that tests this as well?
+
+    nxt::Buffer buf = device.CreateBufferBuilder()
+        .SetSize(4)
+        .SetAllowedUsage(nxt::BufferUsageBit::TransferDst | nxt::BufferUsageBit::Vertex)
+        .SetInitialUsage(nxt::BufferUsageBit::TransferDst)
+        .GetResult();
+
+    uint32_t foo = 0;
+    buf.SetSubData(0, 1, &foo);
+
+    buf.TransitionUsage(nxt::BufferUsageBit::Vertex);
+    ASSERT_DEVICE_ERROR(buf.SetSubData(0, 1, &foo));
+
+    nxt::CommandBuffer cmdbuf = device.CreateCommandBufferBuilder()
+        .TransitionBufferUsage(buf, nxt::BufferUsageBit::TransferDst)
+        .GetResult();
+    queue.Submit(1, &cmdbuf);
+    // buf should be in TransferDst usage
+
+    buf.SetSubData(0, 1, &foo);
+}