Update dawn.h -> webgpu.h, dawn_cpp.h -> webgpu_cpp.h.

Also fix some compile breakages from recent Skia changes.
No changes to Skia API.

Change-Id: Ifd0b1d89fb4ea3cf1f6a7170f2f74614276364ae
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257877
Commit-Queue: Stephen White <senorblanco@chromium.org>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/GrLegacyDirectContext.cpp b/src/gpu/GrLegacyDirectContext.cpp
index 1353001..34002a8 100644
--- a/src/gpu/GrLegacyDirectContext.cpp
+++ b/src/gpu/GrLegacyDirectContext.cpp
@@ -224,12 +224,12 @@
 #endif
 
 #ifdef SK_DAWN
-sk_sp<GrContext> GrContext::MakeDawn(const dawn::Device& device) {
+sk_sp<GrContext> GrContext::MakeDawn(const wgpu::Device& device) {
     GrContextOptions defaultOptions;
     return MakeDawn(device, defaultOptions);
 }
 
-sk_sp<GrContext> GrContext::MakeDawn(const dawn::Device& device, const GrContextOptions& options) {
+sk_sp<GrContext> GrContext::MakeDawn(const wgpu::Device& device, const GrContextOptions& options) {
     sk_sp<GrContext> context(new GrLegacyDirectContext(GrBackendApi::kDawn, options));
 
     context->fGpu = GrDawnGpu::Make(device, options, context.get());