SkiaRenderer Dawn: Use old swapchain API

The new Dawn swapchain API is not implemented yet. Use the old swapchain
path by passing a null wgpu::Surface to CreateSwapChain().

The bug for implementing the new API is https://crbug.com/dawn/269.

Bug: 1021566
Change-Id: I76306856cca919a4e2ef131087163204f41f91ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2075458Reviewed-by: kylechar <kylechar@chromium.org>
Commit-Queue: Sean Gilhuly <sgilhuly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744785}

components/viz/service/display_embedder/skia_output_device_dawn.cc

@@ -57,9 +57,9 @@ bool SkiaOutputDeviceDawn::Reshape(const gfx::Size& size,
   CreateSwapChainImplementation();
   wgpu::SwapChainDescriptor desc;
   desc.implementation = reinterpret_cast<int64_t>(&swap_chain_implementation_);
-  wgpu::Instance instance = context_provider_->GetInstance();
-  wgpu::Surface surface = instance.CreateSurface(nullptr);
-  swap_chain_ = context_provider_->GetDevice().CreateSwapChain(surface, &desc);
+  // TODO(sgilhuly): Use a wgpu::Surface in this call once the Surface-based
+  // SwapChain API is ready.
+  swap_chain_ = context_provider_->GetDevice().CreateSwapChain(nullptr, &desc);
   if (!swap_chain_)
     return false;
   swap_chain_.Configure(kSwapChainFormat, kUsage, size_.width(),