app,app/internal/wm: fold context MakeCurrent/ReleaseCurrent into Lock/Unlock

While here, make context Refresh useful and remove the redundant
MakeCurrent from the window loop.

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

app/internal/wm/gl_js.go

@@ -50,7 +50,9 @@ func (c *context) Present() error {
 	return nil
 }
 
-func (c *context) Lock() {}
+func (c *context) Lock() error {
+	return nil
+}
 
 func (c *context) Unlock() {}
 
@@ -58,12 +60,6 @@ func (c *context) Refresh() error {
 	return nil
 }
 
-func (c *context) MakeCurrent() error {
-	return nil
-}
-
-func (c *context) ReleaseCurrent() {}
-
 func (w *window) NewContext() (Context, error) {
 	return newContext(w)
 }