Implement the webgpu.h swapchains in the frontend and Null backend.

The state-tracking of the webgpu.h swapchain is a bit complicated
because contrary to implementation-based swapchains, they have more
guarantees and a "replacing mechanism". For example instead of hoping
the implementation-based swapchain resize automatically, the
surface-based swapchain needs to be replaced by a new swapchain and
invalidated.

This mechanism of invalidation also needs to be triggered when the last
reference to the surface is lost because we don't want to risk the
application destroying the window from under us.

Adds tests for all the cases of invalidation I could think of apart from
device loss.

Bug: dawn:269

Change-Id: Id515dbb640e13c6e30bb1f1e93b8e54f1e2bba4b
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/15400
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>

src/dawn_native/opengl/DeviceGL.cpp

@@ -96,8 +96,9 @@ namespace dawn_native { namespace opengl {
         const SwapChainDescriptor* descriptor) {
         return new SwapChain(this, descriptor);
     }
-    ResultOrError<SwapChainBase*> Device::CreateSwapChainImpl(
+    ResultOrError<NewSwapChainBase*> Device::CreateSwapChainImpl(
         Surface* surface,
+        NewSwapChainBase* previousSwapChain,
         const SwapChainDescriptor* descriptor) {
         return DAWN_VALIDATION_ERROR("New swapchains not implemented.");
     }

src/dawn_native/opengl/DeviceGL.h

@@ -80,8 +80,9 @@ namespace dawn_native { namespace opengl {
             const ShaderModuleDescriptor* descriptor) override;
         ResultOrError<SwapChainBase*> CreateSwapChainImpl(
             const SwapChainDescriptor* descriptor) override;
-        ResultOrError<SwapChainBase*> CreateSwapChainImpl(
+        ResultOrError<NewSwapChainBase*> CreateSwapChainImpl(
             Surface* surface,
+            NewSwapChainBase* previousSwapChain,
             const SwapChainDescriptor* descriptor) override;
         ResultOrError<TextureBase*> CreateTextureImpl(const TextureDescriptor* descriptor) override;
         ResultOrError<TextureViewBase*> CreateTextureViewImpl(