cc: Add more eviction categories to picture layer impl.

cc/resources/picture_layer_tiling.h

Index: cc/resources/picture_layer_tiling.h
diff --git a/cc/resources/picture_layer_tiling.h b/cc/resources/picture_layer_tiling.h
index a252bafe82dcf8a355c8afb5a4a724169ec6ab8b..d9ae695b265e8572b9d6bb75f673a4be82a02a8c 100644
--- a/cc/resources/picture_layer_tiling.h
+++ b/cc/resources/picture_layer_tiling.h
@@ -57,10 +57,14 @@ class CC_EXPORT PictureLayerTiling {
  public:
   enum EvictionCategory {
     EVENTUALLY,
+    EVENTUALLY_AND_REQUIRED_FOR_ACTIVATION,
     SOON,
+    SOON_AND_REQUIRED_FOR_ACTIVATION,
     NOW,
     NOW_AND_REQUIRED_FOR_ACTIVATION
   };
+  enum { NUM_EVICTION_CATEGORIES = NOW_AND_REQUIRED_FOR_ACTIVATION + 1 };

[vmpstr, 2014/08/14 06:23:48]

I'm not sure what our style guide says about enums anymore :) I prefer this
approach, but if you have another preference I'll be happy to change it.

[reveman, 2014/08/14 09:01:50]

We don't have a nice consistent mechanism for this. I was trying to create this
at one point (https://codereview.chromium.org/22911037/) but never had the time
to make it build on win and push for it as a standard in cc and/or chromium.

The problem with the approach you use here is that one might easily forget to
update NUM_EVICTION_CATEGORIES when adding more enum values.

enum EvictionCategory {
  EVENTUALLY,
  SOON,
  NOW,
  NOW_AND_REQUIRED_FOR_ACTIVATION,
  kEvictionCategoryMax = NOW_AND_REQUIRED_FOR_ACTIVATION
}

is a bit better imo but suffers from the same problem. Adding
NUM_EVICTION_CATEGORIES at the end is another option but the problem with that
is obvious.

I prefer if we avoid array indexing using enum values until we have a nice
mechanism to do this. How about we keep this as before but create a bug for
adding a proper mechanism for using enum values as array indexes and put a TODO
here? You can assign the bug to me and I'll try to finish up that old cl.

[danakj, 2014/08/14 16:55:26]

Security team (tsepez) has been adding a LAST_FOO_BAR to enums like

enum Value {
a
b
LAST_VALUE=b
};

so we should probly be consistent with that.

[vmpstr, 2014/08/14 22:05:50]

Removed this for now, added a TODO instead.

+
   class CC_EXPORT TilingRasterTileIterator {
    public:
     TilingRasterTileIterator();
@@ -336,10 +340,7 @@ class CC_EXPORT PictureLayerTiling {
   bool has_soon_border_rect_tiles_;
   bool has_eventually_rect_tiles_;
 
-  std::vector<Tile*> eventually_eviction_tiles_;
-  std::vector<Tile*> soon_eviction_tiles_;
-  std::vector<Tile*> now_eviction_tiles_;
-  std::vector<Tile*> now_and_required_for_activation_eviction_tiles_;
+  std::vector<Tile*> eviction_tiles_[NUM_EVICTION_CATEGORIES];
   bool eviction_tiles_cache_valid_;
   TreePriority eviction_cache_tree_priority_;