Use the hardware scaler again on Android. Move all DPI handling code from java to app-android.cpp.

ext/native/ui/ui_context.cpp

@@ -97,7 +97,7 @@ Bounds UIContext::GetScissorBounds() {
 void UIContext::ActivateTopScissor() {
 	if (scissorStack_.size()) {
 		const Bounds &bounds = scissorStack_.back();
-		float scale = 1.0f / g_dpi_scale;
+		float scale = pixel_in_dps;
 		int x = scale * bounds.x;
 		int y = scale * bounds.y;
 		int w = scale * bounds.w;