Update from https://crrev.com/312398

cc/resources/tiling_set_raster_queue_required.cc

 // Copyright 2014 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/resources/tiling_set_raster_queue_required.h"
 
 #include <utility>
 
 #include "cc/resources/picture_layer_tiling_set.h"
 #include "cc/resources/tile.h"
 #include "cc/resources/tile_priority.h"
 
 namespace cc {
 
 TilingSetRasterQueueRequired::TilingSetRasterQueueRequired(
     PictureLayerTilingSet* tiling_set,
     RasterTilePriorityQueue::Type type)
     : type_(type) {
   DCHECK_NE(static_cast<int>(type),
             static_cast<int>(RasterTilePriorityQueue::Type::ALL));
 
   // Any type of required tile would only come from a high resolution tiling.
   // The functions that determine this value is
   // PictureLayerTiling::IsTileRequiredFor*, which all return false if the
   // resolution is not HIGH_RESOLUTION.
   PictureLayerTiling* tiling =
       tiling_set->FindTilingWithResolution(HIGH_RESOLUTION);
-  DCHECK(tiling);
+  // If we don't have a high res tiling, then this queue will yield no tiles.
+  // See PictureLayerImpl::CanHaveTilings for examples of when a HIGH_RESOLUTION
+  // tiling would not be generated.
+  if (!tiling)
+    return;
+
   iterator_ = TilingIterator(tiling, &tiling->tiling_data_);
   while (!iterator_.done() && !IsTileRequired(*iterator_))
     ++iterator_;
 }
 
 TilingSetRasterQueueRequired::~TilingSetRasterQueueRequired() {
 }
 
 bool TilingSetRasterQueueRequired::IsEmpty() const {
   return iterator_.done();
@@ skipping 88 matching lines @@
     // in the NOW bin, which means that it can be required.
     break;
   }
 
   if (current_tile_)
     tiling_->UpdateTileAndTwinPriority(current_tile_);
   return *this;
 }
 
 }  // namespace cc