[regression] Imagery zooming in causes black tiles to appear briefly

[RicoElectrico]

What steps will reproduce the problem?

1. Use an imagery source
2. Zoom in quickly

What is the expected result?

While zooming in, tiles that aren't yet loaded have upscaled lower-zoom tiles as a placeholder

What happens instead?

Black squares flash briefly where tiles aren't loaded yet.

Please provide any additional information below. Attach a screenshot if possible.

This is a regression in the latest release, probably due to the introduction of layer filters.

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2016-04-28 12:48:16 +0200 (Thu, 28 Apr 2016)
Build-Date:2016-04-28 10:51:36
Revision:10161
Relative:URL: ^/trunk

Identification: JOSM/1.5 (10161 pl) Windows 8.1 64-Bit
Memory Usage: 543 MB / 910 MB (165 MB allocated, but free)
Java version: 1.8.0_77-b03, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM

Plugins:
- BuildingGeneralization (UNKNOWN)
- FastDraw (31895)
- FixAddresses (31772)
- HouseNumberTaggingTool (31772)
- OpeningHoursEditor (31772)
- PicLayer (31895)
- ShowInGoogleMaps (8)
- SimplifyArea (31895)
- Tracer2 (32042)
- alignways (31895)
- apache-commons (31895)
- buildings_tools (31895)
- contourmerge (1014)
- dataimport (31772)
- editgpx (32148)
- ejml (31895)
- geotools (31895)
- gson (31895)
- imagery_offset_db (32046)
- importvec (31772)
- jogl (1.0.46)
- josm-plugin-opengl (1440156917)
- jts (31772)
- kendzi3d (1.0.190.1)
- kendzi3d-resources (0.0.1)
- log4j (31895)
- mapdust (31772)
- measurement (31895)
- opendata (32139)
- pbf (32128)
- photo_geotagging (31895)
- poly (31772)
- reverter (32005)
- splinex (31895)
- surveyor2 (29210)
- terracer (31895)
- todo (29154)
- undelete (31895)
- utilsplugin2 (32099)
- wikipedia (32114)

Tagging presets:
- http://somewhere.dk/email/josm/source.xml

Map paint styles:
- https://github.com/bastik/mapcss-tools/raw/osm/mapnik2mapcss/osm-results/mapnik.zip
- https://github.com/gmgeo/osmic-josm-style/archive/master.zip

Validator rules:
- %UserProfile%\Desktop\skroty.validator.mapcss

[wiktorn]

Not due to layer filters but indeed, there is such a bug. Got a fix for it.

[wiktorn]

In 10168/josm:

Process and render the tiles that are not loaded, so placeholder graphics will be properly rendered.

Closes: #12812