Reland r206537 - cc: Don't return mailboxes if the TextureLayer is removed from the tree.

cc/layers/texture_layer_impl.cc

Index: cc/layers/texture_layer_impl.cc
diff --git a/cc/layers/texture_layer_impl.cc b/cc/layers/texture_layer_impl.cc
index ad28757aac66fe2ab910f4effacda2c689746c56..3ded0c92a53011c9766176381389de60b1aa15b0 100644
--- a/cc/layers/texture_layer_impl.cc
+++ b/cc/layers/texture_layer_impl.cc
@@ -34,8 +34,6 @@ TextureLayerImpl::~TextureLayerImpl() { FreeTextureMailbox(); }
 
 void TextureLayerImpl::SetTextureMailbox(const TextureMailbox& mailbox) {
   DCHECK(uses_mailbox_);
-  if (own_mailbox_)
-    DCHECK(!mailbox.IsValid() || !mailbox.Equals(texture_mailbox_));
   FreeTextureMailbox();
   texture_mailbox_ = mailbox;
   own_mailbox_ = true;