mac: Remove code to support OS X 10.10 in //gpu

Bug: 1153883
Change-Id: I91cabcc04d78ad3d3d97bdb55855bedc9eb92114
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2571805Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833430}

gpu/command_buffer/service/shared_image_backing_factory_iosurface.mm

@@ -35,8 +35,8 @@ namespace gpu {
 
 namespace {
 
-base::scoped_nsprotocol<id<MTLTexture>> API_AVAILABLE(macos(10.11))
-    CreateMetalTexture(id<MTLDevice> mtl_device,
+base::scoped_nsprotocol<id<MTLTexture>> CreateMetalTexture(
+    id<MTLDevice> mtl_device,
     IOSurfaceRef io_surface,
     const gfx::Size& size,
     viz::ResourceFormat format) {
@@ -175,7 +175,6 @@ SharedImageBackingFactoryIOSurface::ProduceSkiaPromiseTextureMetal(
     SharedImageBacking* backing,
     scoped_refptr<SharedContextState> context_state,
     scoped_refptr<gl::GLImage> image) {
-  if (@available(macOS 10.11, *)) {
   DCHECK(context_state->GrContextIsMetal());
 
   base::ScopedCFTypeRef<IOSurfaceRef> io_surface =
@@ -193,8 +192,6 @@ SharedImageBackingFactoryIOSurface::ProduceSkiaPromiseTextureMetal(
       GrBackendTexture(backing->size().width(), backing->size().height(),
                        GrMipMapped::kNo, info);
   return SkPromiseImageTexture::Make(gr_backend_texture);
-  }
-  return nullptr;
 }
 
 // static