Dawn: fix Device leak in DawnTestContext.

The C WGPUDevice returned by CreateDevice needs an Acquire call to
ensure it's correctly refcounted.

Bug: skia:10291

Change-Id: If5d917165b5846bea1472f24aa12db2db7f3a9e6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/292958
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>

tools/gpu/dawn/DawnTestContext.cpp

@@ -88,7 +88,7 @@ public:
         std::vector<dawn_native::Adapter> adapters = instance.GetAdapters();
         for (dawn_native::Adapter adapter : adapters) {
             if (adapter.GetBackendType() == type) {
-                return adapter.CreateDevice();
+                return wgpu::Device::Acquire(adapter.CreateDevice());
             }
         }
         return nullptr;