Add more out of line copy ctors for complex classes.

cc/tiles/prioritized_tile.cc

 // Copyright 2015 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/tiles/prioritized_tile.h"
 
 #include "cc/debug/traced_value.h"
 #include "cc/tiles/picture_layer_tiling.h"
 
 namespace cc {
 
 PrioritizedTile::PrioritizedTile() : tile_(nullptr), is_occluded_(false) {}
 
 PrioritizedTile::PrioritizedTile(
     Tile* tile,
     scoped_refptr<DisplayListRasterSource> raster_source,
     const TilePriority priority,
     bool is_occluded)
     : tile_(tile),
       raster_source_(std::move(raster_source)),
       priority_(priority),
       is_occluded_(is_occluded) {}
 
+PrioritizedTile::PrioritizedTile(const PrioritizedTile& other) = default;
+
 PrioritizedTile::~PrioritizedTile() {
 }
 
 void PrioritizedTile::AsValueInto(base::trace_event::TracedValue* value) const {
   tile_->AsValueInto(value);
 
   TracedValue::SetIDRef(raster_source().get(), value, "picture_pile");
 
   value->BeginDictionary("combined_priority");
   priority().AsValueInto(value);
   value->SetBoolean("is_occluded", is_occluded_);
   value->EndDictionary();
 
   value->SetString("resolution", TileResolutionToString(priority().resolution));
 }
 
 }  // namespace cc