Support resize in Android Viewer App

tools/viewer/sk_app/android/GLWindowContext_android.h

 
 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef GLWindowContext_android_DEFINED
 #define GLWindowContext_android_DEFINED
 
 #include "../GLWindowContext.h"
 #include "Window_android.h"
 
 #include <EGL/egl.h>
 
+struct ANativeWindow;
+
 namespace sk_app {
 
 class GLWindowContext_android : public GLWindowContext {
 public:
     friend GLWindowContext* GLWindowContext::Create(void* platformData, const DisplayParams&);
 
     ~GLWindowContext_android() override;
 
     void onSwapBuffers() override;
 
     void onInitializeContext(void*, const DisplayParams&) override;
     void onDestroyContext() override;
 
 private:
     GLWindowContext_android(void*, const DisplayParams&);
 
     EGLDisplay fDisplay;
     EGLContext fEGLContext;
     EGLSurface fSurface;
+
+    // For setDisplayParams and resize which call onInitializeContext with null platformData
+    ANativeWindow* fNativeWindow = nullptr;
 };
 
 
 }
 
 #endif