Use Windowing system-specific WindowContext factories.

tools/viewer/sk_app/android/GLWindowContext_android.h

Index: tools/viewer/sk_app/android/GLWindowContext_android.h
diff --git a/tools/viewer/sk_app/android/GLWindowContext_android.h b/tools/viewer/sk_app/android/GLWindowContext_android.h
deleted file mode 100644
index 5f4c031ed1b44f22c8782574a08a4aafe6541722..0000000000000000000000000000000000000000
--- a/tools/viewer/sk_app/android/GLWindowContext_android.h
+++ /dev/null
@@ -1,45 +0,0 @@
-
-/*
- * 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