Implement Raster Backend on Android Viewer App

tools/viewer/sk_app/android/Window_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 Window_android_DEFINED
 #define Window_android_DEFINED
 
@@ skipping 26 matching lines @@
     void setUIState(const Json::Value& state) override;
 
     void paintIfNeeded();
 
     bool scaleContentToFit() const override { return true; }
     bool supportsContentRect() const override { return true; }
     SkRect getContentRect() override { return fContentRect; }
     void setContentRect(int l, int t, int r, int b) { fContentRect.set(l,t,r,b); }
 
 private:
-    // We need fNativeWindow for attaching with another backend.
-    // (in that case, attach is called without initDisplay being called later)
-    ANativeWindow* fNativeWindow = nullptr;
     SkiaAndroidApp* fSkiaAndroidApp = nullptr;
     SkRect fContentRect;
     DisplayParams fDisplayParams;
     BackendType fBackendType;
 };
 
 }   // namespace sk_app
 
 #endif