Introduce [Render|Compute]PassEncoder.

This splits off part of CommandBufferBuilder in separate
RenderPassEncoder and ComputePassEncoder objects. To match the WebGPU
IDL and factor some code, both these encoders inherit from
ProgrammablePassEncoder.

These encoders are pure frontend objects and record into the
CommandBufferBuilder command allocator objects, so no changes to the
backends were needed.

Error handling is still ew, because the "builder" mechanism we had
doesn't allow for "split builders". Nicer error handling will have to
wait on Dawn matching WebGPU.

All the tests and samples were updated to the new structure.

BUG=dawn:5

Change-Id: I5f5d4ad866e2c07fedd1ba7a122258c6610941f1
Reviewed-on: https://dawn-review.googlesource.com/1543
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/dawn_native/ComputePassEncoder.cpp

@@ -0,0 +1,52 @@
+// Copyright 2018 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/ComputePassEncoder.h"
+
+#include "dawn_native/CommandBuffer.h"
+#include "dawn_native/Commands.h"
+#include "dawn_native/ComputePipeline.h"
+
+namespace dawn_native {
+
+    ComputePassEncoderBase::ComputePassEncoderBase(DeviceBase* device,
+                                                   CommandBufferBuilder* topLevelBuilder,
+                                                   CommandAllocator* allocator)
+        : ProgrammablePassEncoder(device, topLevelBuilder, allocator) {
+    }
+
+    void ComputePassEncoderBase::Dispatch(uint32_t x, uint32_t y, uint32_t z) {
+        if (mTopLevelBuilder->ConsumedError(ValidateCanRecordCommands())) {
+            return;
+        }
+
+        DispatchCmd* dispatch = mAllocator->Allocate<DispatchCmd>(Command::Dispatch);
+        new (dispatch) DispatchCmd;
+        dispatch->x = x;
+        dispatch->y = y;
+        dispatch->z = z;
+    }
+
+    void ComputePassEncoderBase::SetComputePipeline(ComputePipelineBase* pipeline) {
+        if (mTopLevelBuilder->ConsumedError(ValidateCanRecordCommands())) {
+            return;
+        }
+
+        SetComputePipelineCmd* cmd =
+            mAllocator->Allocate<SetComputePipelineCmd>(Command::SetComputePipeline);
+        new (cmd) SetComputePipelineCmd;
+        cmd->pipeline = pipeline;
+    }
+
+}  // namespace dawn_native