cc: add DCHECKs of tile in GPUMemoryUsageInBytes and PushPropertiesTo

cc/layers/tiled_layer_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/layers/tiled_layer_impl.h"
 
 #include "base/basictypes.h"
 #include "base/strings/stringprintf.h"
 #include "cc/base/math_util.h"
 #include "cc/debug/debug_colors.h"
@@ skipping 94 matching lines @@
 }
 
 size_t TiledLayerImpl::GPUMemoryUsageInBytes() const {
   size_t amount = 0;
   const size_t kMemoryUsagePerTileInBytes =
       4 * tiler_->tile_size().width() * tiler_->tile_size().height();
   for (LayerTilingData::TileMap::const_iterator iter = tiler_->tiles().begin();
        iter != tiler_->tiles().end();
        ++iter) {
     const DrawableTile* tile = static_cast<DrawableTile*>(iter->second);
-    if (!tile || !tile->resource_id())
+    DCHECK(tile);
+    if (!tile->resource_id())
       continue;
     amount += kMemoryUsagePerTileInBytes;
   }
   return amount;
 }
 
 void TiledLayerImpl::PushPropertiesTo(LayerImpl* layer) {
   LayerImpl::PushPropertiesTo(layer);
 
   TiledLayerImpl* tiled_layer = static_cast<TiledLayerImpl*>(layer);
 
   tiled_layer->set_skips_draw(skips_draw_);
   tiled_layer->SetTilingData(*tiler_);
 
   for (LayerTilingData::TileMap::const_iterator iter = tiler_->tiles().begin();
        iter != tiler_->tiles().end();
        ++iter) {
     int i = iter->first.first;
     int j = iter->first.second;
     DrawableTile* tile = static_cast<DrawableTile*>(iter->second);
-
+    DCHECK(tile);
     tiled_layer->PushTileProperties(i,
                                     j,
                                     tile->resource_id(),
                                     tile->opaque_rect(),
                                     tile->contents_swizzled());
   }
 }
 
 bool TiledLayerImpl::WillDraw(DrawMode draw_mode,
                               ResourceProvider* resource_provider) {
@@ skipping 160 matching lines @@
 
 void TiledLayerImpl::ReleaseResources() {
   tiler_->reset();
 }
 
 const char* TiledLayerImpl::LayerTypeAsString() const {
   return "cc::TiledLayerImpl";
 }
 
 }  // namespace cc