Implement Raster Backend on Android Viewer App

tools/viewer/sk_app/android/RasterWindowContext_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 RasterWindowContext_android_DEFINED
+#define RasterWindowContext_android_DEFINED
+
+#include <android/native_window_jni.h>
+
+#include "../RasterWindowContext.h"
+
+namespace sk_app {
+
+class RasterWindowContext_android : public RasterWindowContext {
+public:
+    RasterWindowContext_android(void* platformData, const DisplayParams& params);
+
+protected:
+    void onSwapBuffers(sk_sp<SkImage>) override;
+
+private:
+    ANativeWindow* fNativeWindow = nullptr;
+};
+
+}   // namespace sk_app
+
+#endif