Nyall Dawson 86ab3022b5 Remove layer extent and statistic variables from processing contexts
These variables take a lot of time to calculate and cause lots of
lengthy hangs in processing. (Eg add some moderately large rasters
to a project, then try to run any processing algorithm and QGIS
will freeze).

The layer extent can already be used in expressions via the
layer_property function, which only evalutes the extent if required
and only for layers it is used for.

The band stats for raster layers should be moved to a
band_statistic function in core which behaves the same way.
2016-11-22 11:17:38 +10:00
..
2016-11-12 13:31:44 +02:00