Revert "[ios] Updates for Dawn"

This reverts commit c5ad2b6.

Reason for revert: causing build failures on ios-blink-dbg-fyi.
Example:
https://ci.chromium.org/ui/p/chromium/builders/ci/ios-blink-dbg-fyi/7487/overview

Original change's description:
> [ios] Updates for Dawn
>
> Generalizes some build flags and gn setup.
>
> Bug: 1411704
> Change-Id: Iac7b59a4457e76d513eb7220bb719d978592ef3d
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4650848
> Reviewed-by: Corentin Wallez <cwallez@chromium.org>
> Reviewed-by: Avi Drissman <avi@chromium.org>
> Commit-Queue: Ian Vollick <vollick@chromium.org>
> Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1164850}

Bug: 1411704
Change-Id: I29b213cba7d0fbbfc1524c2dc7f3faf580cbf548
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4661236
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Owners-Override: Avi Drissman <avi@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1165069}

components/viz/service/display_embedder/skia_output_surface_impl_on_gpu.cc

@@ -2087,14 +2087,12 @@ bool SkiaOutputSurfaceImplOnGpu::InitializeForDawn() {
         GetDidSwapBuffersCompleteCallback());
     AddChildWindowToBrowser(output_device->GetChildSurfaceHandle());
     output_device_ = std::move(output_device);
-#elif BUILDFLAG(IS_APPLE)
+#elif BUILDFLAG(IS_MAC)
     presenter_ = dependency_->CreatePresenter(weak_ptr_factory_.GetWeakPtr(),
                                               gl::GLSurfaceFormat());
-#if BUILDFLAG(IS_MAC)
     if (features::UseGpuVsync()) {
       presenter_->SetVSyncDisplayID(renderer_settings_.display_id);
     }
-#endif
     output_device_ = std::make_unique<SkiaOutputDeviceBufferQueue>(
         std::make_unique<OutputPresenterGL>(
             presenter_, dependency_, shared_image_factory_.get(),

gpu/command_buffer/service/dawn_context_provider.cc

@@ -52,7 +52,7 @@ wgpu::BackendType GetDefaultBackendType() {
              : wgpu::BackendType::D3D11;
 #elif BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS)
   return wgpu::BackendType::Vulkan;
-#elif BUILDFLAG(IS_APPLE)
+#elif BUILDFLAG(IS_MAC)
   return wgpu::BackendType::Metal;
 #else
   NOTREACHED();

ui/gl/features.gni

@@ -18,8 +18,8 @@ declare_args() {
 
   # Should Dawn support be compiled to back the WebGPU implementation?
   # Also controls linking Dawn dependencies in such as SPIRV-Tools/SPIRV-Cross.
-  use_dawn = is_apple || is_win || is_chromeos_ash ||
-             (is_linux && !is_castos) || is_chromeos_lacros ||
+  use_dawn = is_mac || is_win || is_chromeos_ash || (is_linux && !is_castos) ||
+             is_chromeos_lacros ||
              (is_android && target_cpu != "x86" && target_cpu != "x64")
 
   # Should Dawn test binaries (unittests, end2end_tests, perf_tests) be built?