BIconButton: Use BControlLook::ComposeIconSize().

This isn't perfect as the margins are not yet scaled,
but at least the toolbar buttons in WebPositive now
change with the font size.

src/kits/shared/IconButton.cpp

@@ -310,7 +310,8 @@ BIconButton::SetIcon(int32 resourceID)
 	const void* data = resources.LoadResource(B_VECTOR_ICON_TYPE, resourceID,
 		&size);
 	if (data != NULL) {
-		BBitmap bitmap(BRect(0, 0, 31, 31), B_BITMAP_NO_SERVER_LINK, B_RGBA32);
+		BBitmap bitmap(BRect(BPoint(0, 0), be_control_look->ComposeIconSize(32)),
+			B_BITMAP_NO_SERVER_LINK, B_RGBA32);
 		status = bitmap.InitCheck();
 		if (status != B_OK)
 			return status;