cc: Remove tilings from recycle tree when active tree removes them.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 02fb92fb735dce8d5048487eebe38ab6800c7706..9259dc4afe3321419c18eb88b465ca1b9e74b4b2 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -1201,6 +1201,10 @@ void PictureLayerImpl::CleanUpTilingsOnActiveLayer(
     to_remove.push_back(tiling);
   }
 
+  if (to_remove.empty())
+    return;
+
+  // Remove tilings on this tree and the twin tree.
   for (size_t i = 0; i < to_remove.size(); ++i) {
     const PictureLayerTiling* twin_tiling = GetTwinTiling(to_remove[i]);
     // Only remove tilings from the twin layer if they have
@@ -1211,9 +1215,19 @@ void PictureLayerImpl::CleanUpTilingsOnActiveLayer(
     CHECK_NE(HIGH_RESOLUTION, to_remove[i]->resolution());
     tilings_->Remove(to_remove[i]);
   }
-  DCHECK_GT(tilings_->num_tilings(), 0u);
 
+  DCHECK_GT(tilings_->num_tilings(), 0u);
   SanityCheckTilingState();
+
+  // Also remove tilings from the recycle tree to ensure that recycle tree
+  // doesn't have any unshared tiles.
+  PictureLayerImpl* recycled_twin = static_cast<PictureLayerImpl*>(
+      layer_tree_impl()->FindRecycleTreeLayerById(id()));
+  if (!recycled_twin)
+    return;
+
+  for (size_t i = 0; i < to_remove.size(); ++i)
+    recycled_twin->RemoveTiling(to_remove[i]->contents_scale());

[danakj, 2014/07/17 22:22:49]

er, wait, to_remove[i] is a use-after-free here, cuz we Remove()'d it above

[vmpstr, 2014/07/17 22:30:59]

Hmm.. that's not good. Good thing my testing worked just fine? I've changed it
around a bit. Good catch.

Should we also change for (i from 0 to to_remove.size()) to be more like

while (!to_remove.empty()) { tiling = to_remove.back() .. to_remove.pop_back() }

to avoid people like me messing this up in the future?

 }
 
 float PictureLayerImpl::MinimumContentsScale() const {
@@ -1261,6 +1275,10 @@ bool PictureLayerImpl::CanHaveTilingWithScale(float contents_scale) const {
 
 void PictureLayerImpl::SanityCheckTilingState() const {
 #if DCHECK_IS_ON
+  // Recycle tree doesn't have any restrictions.
+  if (layer_tree_impl()->IsRecycleTree())
+    return;
+
   if (!CanHaveTilings()) {
     DCHECK_EQ(0u, tilings_->num_tilings());
     return;