Change: Standardize progress bar layout.

Progress bars are drawn differently depending on when it was added, with
different layouts and sizes.

This change adds a standard padding size to use, and makes all progress
bars visually similar, with scaled padding.

src/network/network_content_gui.h

@@ -33,6 +33,7 @@ public:
 	BaseNetworkContentDownloadStatusWindow(WindowDesc *desc);
 
 	void Close() override;
+	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override;
 	void DrawWidget(const Rect &r, int widget) const override;
 	void OnDownloadProgress(const ContentInfo *ci, int bytes) override;
 };