More conservative source pixbuf caching: Bug #715198
Prior source pixbuf (untransformed, full-sized decoded images) cache was per-photo, holding onto the source pixbuf for 180s. For casual browsing it wasn't onerous, but if the photos were loaded quickly in succession (either with the photo viewer or, worse, via the programmatic thumbnail regenerator) memory usage would climb into the gigabytes. This uses a more conservative source pixbuf cache, holding only a few at a time and releasing them much more quickly. The PixbufCache class does a better job of long-term pixbuf caching by holding onto scaled images rather than full-sized.
Showing with 169 additions and 72 deletions