Temporarily suppress element id collision DCHECK for SPV2

cc/trees/layer_tree_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 536 matching lines @@
     return;
 
   TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("compositor-worker"),
                "LayerTreeImpl::AddToElementMap", "element",
                element_id.AsValue().release(), "layer_id", layer->id());
 
 #if DCHECK_IS_ON()
   LayerImpl* existing_layer = LayerByElementId(element_id);
   bool element_id_collision_detected =
       existing_layer && existing_layer != layer;
-  DCHECK(!element_id_collision_detected);
+
+  // TODO(pdr): Remove this suppression and always check for id collisions.
+  // This is a temporary suppression for SPV2 which generates unnecessary
+  // layers that collide. Remove once crbug.com/693693 is fixed.
+  if (!settings().use_layer_lists)
+    DCHECK(!element_id_collision_detected);
 #endif
 
   element_layers_map_[element_id] = layer->id();
 
   layer_tree_host_impl_->mutator_host()->RegisterElement(
       element_id,
       IsActiveTree() ? ElementListType::ACTIVE : ElementListType::PENDING);
 }
 
 void LayerTreeImpl::RemoveFromElementMap(LayerImpl* layer) {
@@ skipping 1524 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc