LibWeb: Change paint_all_borders() to accept only device pixel values

By consistently accepting only device pixel values instead of a mix of
CSSPixels and DevicePixels values, we can simplify the implementation
of paint_border() and paint_all_borders().

Userland/Libraries/LibWeb/Painting/BordersData.cpp

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2023, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Painting/BordersData.h>
+#include <LibWeb/Painting/PaintContext.h>
+
+namespace Web::Painting {
+
+BordersDataDevicePixels BordersData::to_device_pixels(PaintContext const& context) const
+{
+    return BordersDataDevicePixels {
+        BorderDataDevicePixels {
+            top.color,
+            top.line_style,
+            context.enclosing_device_pixels(top.width).value() },
+        BorderDataDevicePixels {
+            right.color,
+            right.line_style,
+            context.enclosing_device_pixels(right.width).value() },
+        BorderDataDevicePixels {
+            bottom.color,
+            bottom.line_style,
+            context.enclosing_device_pixels(bottom.width).value() },
+        BorderDataDevicePixels {
+            left.color,
+            left.line_style,
+            context.enclosing_device_pixels(left.width).value() }
+    };
+}
+
+}