gpu/headless: remove useless headless_gl.go abstraction

There is no longer any shared code between OpenGL backends (unlike
EGL backends).

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/headless/headless_darwin.go

@@ -22,7 +22,7 @@ type nsContext struct {
 	ctx C.CFTypeRef
 }
 
-func newGLContext() (context, error) {
+func newContext() (context, error) {
 	ctx := C.gio_headless_newContext()
 	return &nsContext{ctx: ctx}, nil
 }

gpu/headless/headless_egl.go

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: Unlicense OR MIT
 
-//go:build linux || freebsd || windows || openbsd
+//go:build linux || freebsd || openbsd
-// +build linux freebsd windows openbsd
+// +build linux freebsd openbsd
 
 package headless
 
@@ -9,6 +9,6 @@ import (
 	"gioui.org/internal/egl"
 )
 
-func newGLContext() (context, error) {
+func newContext() (context, error) {
 	return egl.NewContext(egl.EGL_DEFAULT_DISPLAY)
 }

gpu/headless/headless_gl.go

@@ -1,10 +0,0 @@
-// SPDX-License-Identifier: Unlicense OR MIT
-
-//go:build !windows
-// +build !windows
-
-package headless
-
-func newContext() (context, error) {
-	return newGLContext()
-}

gpu/headless/headless_js.go

@@ -14,7 +14,7 @@ type jsContext struct {
 	ctx js.Value
 }
 
-func newGLContext() (context, error) {
+func newContext() (context, error) {
 	doc := js.Global().Get("document")
 	cnv := doc.Call("createElement", "canvas")
 	ctx := cnv.Call("getContext", "webgl2")