cc: Implement tiling iterator based on pyramid sequence.

cc/tiles/tiling_set_raster_queue_required.cc

Index: cc/tiles/tiling_set_raster_queue_required.cc
diff --git a/cc/tiles/tiling_set_raster_queue_required.cc b/cc/tiles/tiling_set_raster_queue_required.cc
index b0173c92326aa0644bf4b28044f1e5226687ce58..36cdd8539d6b1a54de5d93a7e678779e8d99ffae 100644
--- a/cc/tiles/tiling_set_raster_queue_required.cc
+++ b/cc/tiles/tiling_set_raster_queue_required.cc
@@ -113,12 +113,25 @@ TilingSetRasterQueueRequired::TilingIterator::TilingIterator(
   ++(*this);
 }
 
+TilingSetRasterQueueRequired::TilingIterator::TilingIterator(
+    const TilingSetRasterQueueRequired::TilingIterator& other) = default;
+
+TilingSetRasterQueueRequired::TilingIterator::TilingIterator(
+    TilingSetRasterQueueRequired::TilingIterator&& other) = default;
+
 TilingSetRasterQueueRequired::TilingIterator::~TilingIterator() {
 }
 
 TilingSetRasterQueueRequired::TilingIterator&
-    TilingSetRasterQueueRequired::TilingIterator::
-    operator++() {
+TilingSetRasterQueueRequired::TilingIterator::operator=(
+    const TilingSetRasterQueueRequired::TilingIterator& other) = default;
+
+TilingSetRasterQueueRequired::TilingIterator&
+TilingSetRasterQueueRequired::TilingIterator::operator=(
+    TilingSetRasterQueueRequired::TilingIterator&& other) = default;
+
+TilingSetRasterQueueRequired::TilingIterator&
+    TilingSetRasterQueueRequired::TilingIterator::operator++() {
   Tile* tile = nullptr;
   while (true) {
     ++visible_iterator_;