jni: replace True and False with more convenient Bool function

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

cmd/tailscale/main.go

@@ -468,10 +468,7 @@ func (a *App) notify(state BackendState) {
 	case a.updates <- struct{}{}:
 	default:
 	}
-	ready := jni.False
-	if state.State >= ipn.Stopped {
-		ready = jni.True
-	}
+	ready := jni.Bool(state.State >= ipn.Stopped)
 	if err := a.callVoidMethod(a.appCtx, "setTileReady", "(Z)V", jni.Value(ready)); err != nil {
 		fatalErr(err)
 	}
@@ -480,10 +477,7 @@ func (a *App) notify(state BackendState) {
 func (a *App) setPrefs(prefs *ipn.Prefs) {
 	a.mu.Lock()
 	a.prefs = prefs
-	wantRunning := jni.True
-	if !prefs.WantRunning {
-		wantRunning = jni.False
-	}
+	wantRunning := jni.Bool(prefs.WantRunning)
 	a.mu.Unlock()
 	if err := a.callVoidMethod(a.appCtx, "setTileStatus", "(Z)V", jni.Value(wantRunning)); err != nil {
 		fatalErr(err)

jni/jni.go

@@ -64,11 +64,6 @@ type (
 	Value     uint64 // All JNI types fit into 64-bits.
 )
 
-const (
-	True  Boolean = C.JNI_TRUE
-	False Boolean = C.JNI_FALSE
-)
-
 func env(e *Env) *C.JNIEnv {
 	return (*C.JNIEnv)(unsafe.Pointer(e))
 }
@@ -96,6 +91,13 @@ func Do(vm *JVM, f func(env *Env) error) error {
 	return f((*Env)(unsafe.Pointer(env)))
 }
 
+func Bool(b bool) Boolean {
+	if b {
+		return C.JNI_TRUE
+	}
+	return C.JNI_FALSE
+}
+
 func varArgs(args []Value) *C.jvalue {
 	if len(args) == 0 {
 		return nil