fdo#31525 Dialogues now have an appropriate background in OSX

The proper background is now set using HIThemeBackground.

Change-Id: I71e4287273f7345a18eee4c4fc494eea10f2deb2
Reviewed-on: https://gerrit.libreoffice.org/4287Reviewed-by: Thorsten Behrens <tbehrens@suse.com>
Tested-by: Thorsten Behrens <tbehrens@suse.com>

vcl/aqua/source/gdi/salnativewidgets.cxx

@@ -522,7 +522,7 @@ sal_Bool AquaSalGraphics::drawNativeControl(ControlType nType,
             HIThemeBackgroundDrawInfo aThemeBackgroundInfo;
             aThemeBackgroundInfo.version = 0;
             aThemeBackgroundInfo.state = getState( nState );
-            aThemeBackgroundInfo.kind = kThemeBrushDialogBackgroundInactive;
+            aThemeBackgroundInfo.kind = kThemeBrushDialogBackgroundActive;
             // FIXME: without this magical offset there is a 2 pixel black border on the right and bottom
             rc.size.width += 2;
             rc.size.height += 2;