reduced canvas framebuffer resolution for hdpi, update android project

src/node_canvas.h

@@ -8,6 +8,7 @@ public:
     std::unique_ptr<Canvas> m_canvas;
     RTT m_blender_rtt;
     RTT m_cache_rtt;
+    RTT m_rtt;
     Texture2D m_blender_bg;
     Sampler m_sampler;
     Sampler m_sampler_linear;