cc: Implement tiling iterator based on pyramid sequence.

cc/base/reverse_spiral_iterator.cc

Index: cc/base/reverse_spiral_iterator.cc
diff --git a/cc/base/reverse_spiral_iterator.cc b/cc/base/reverse_spiral_iterator.cc
index a0d836878dddefdab0377249ba895ce75e1479aa..6b4560001c3a40305c6b85fcd6b0a158b8857a16 100644
--- a/cc/base/reverse_spiral_iterator.cc
+++ b/cc/base/reverse_spiral_iterator.cc
@@ -77,6 +77,20 @@ ReverseSpiralIterator::ReverseSpiralIterator(
   ++(*this);
 }
 
+ReverseSpiralIterator::ReverseSpiralIterator(
+    const ReverseSpiralIterator::ReverseSpiralIterator& other) = default;
+
+ReverseSpiralIterator::ReverseSpiralIterator(
+    ReverseSpiralIterator::ReverseSpiralIterator&& other) = default;
+
+ReverseSpiralIterator::~ReverseSpiralIterator() = default;
+
+ReverseSpiralIterator& ReverseSpiralIterator::operator=(
+    const ReverseSpiralIterator::ReverseSpiralIterator& other) = default;
+
+ReverseSpiralIterator& ReverseSpiralIterator::operator=(
+    ReverseSpiralIterator::ReverseSpiralIterator&& other) = default;
+
 ReverseSpiralIterator::operator bool() const {
   return index_x_ != -1 && index_y_ != -1;
 }