cmd/ebitenmobile: Use an explict way to detect context lost on Android

Fixes #1176

cmd/ebitenmobile/gobind.go

@@ -751,6 +751,7 @@ class EbitenSurfaceView extends GLSurfaceView {
 
         @Override
         public void onSurfaceCreated(GL10 gl, EGLConfig config) {
+            Ebitenmobileview.onContextLost();
         }
 
         @Override

internal/restorable/const_android.go

@@ -0,0 +1,19 @@
+// Copyright 2020 The Ebiten Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package restorable
+
+const needsDisposingWhenRestoring = true
+
+const canDetectContextLostExplicitly = true

internal/restorable/const_others.go

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build !android
 // +build !js
 
 package restorable

mobile/ebitenmobileview/mobile.go

@@ -30,6 +30,7 @@ import (
 	"sync"
 
 	"github.com/hajimehoshi/ebiten"
+	"github.com/hajimehoshi/ebiten/internal/restorable"
 	"github.com/hajimehoshi/ebiten/internal/uidriver/mobile"
 )
 
@@ -89,3 +90,7 @@ func Suspend() {
 func Resume() {
 	mobile.Get().SetForeground(true)
 }
+
+func OnContextLost() {
+	restorable.OnContextLost()
+}