cc: Add some debugging info to failing DCHECK in PictureLayerTilingSet

cc/resources/picture_layer_tiling_set.cc

Index: cc/resources/picture_layer_tiling_set.cc
diff --git a/cc/resources/picture_layer_tiling_set.cc b/cc/resources/picture_layer_tiling_set.cc
index 779e2c08e9e6d994b9f4f7e9c25635c42efc8662..a6b0a287fcce6fb301fa7b4c065c68a8d530b863 100644
--- a/cc/resources/picture_layer_tiling_set.cc
+++ b/cc/resources/picture_layer_tiling_set.cc
@@ -124,7 +124,10 @@ void PictureLayerTilingSet::UpdateTilingsToCurrentRasterSource(
     // When commiting from the main thread the high res tiling may get dropped,
     // but when cloning to the active tree, there should always be one.
     if (twin_set)

[vmpstr, 2015/02/05 18:26:33]

nit: wrap in braces please

[danakj, 2015/02/05 18:32:03]

Done.

-      DCHECK_EQ(1u, num_high_res);
+      DCHECK_EQ(1u, num_high_res)
+          << " num tilings on active: " << tilings_.size()

[vmpstr, 2015/02/05 18:26:33]

Maybe also tilings_->NumHighResTilings() for both this and twin?

[danakj, 2015/02/05 18:32:03]

Done.

+          << " num tilings on pending: " << twin_set->tilings_.size()
+          << " are on active tree: " << (client_->GetTree() == ACTIVE_TREE);
   }
 #endif
 }