EXA: Offscreen memory eviction improvements.

* Make sure available areas are considered to have no eviction cost. This seems
  to help for https://bugs.freedesktop.org/show_bug.cgi?id=15513 but I'm afraid
  that may just be coincidence.
* Only calculate eviction cost of each area once for each eviction pass.
  Safeguard against potential (though unlikely) division by zero.
* Cosmetic enhancements: Name eviction cost related variables 'cost' instead of
  'score' to emphasize that smaller values are better, update Doxygen file
  comment to the way eviction works now.

1 files changed, 2 insertions, 0 deletions

diff --git a/exa/exa.h b/exa/exa.h
index 97ae6c0a5..256209418 100644
--- a/exa/exa.h
+++ b/exa/exa.h
@@ -64,6 +64,8 @@ struct _ExaOffscreenArea {
     ExaOffscreenState   state;
 
     ExaOffscreenArea    *next;
+
+    unsigned            eviction_cost;
 };
 
 /**