[layoutng] Allow testing NGBox without a LayoutObject

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc

Index: third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc b/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc
index a4a77c0b29ca41be579feb73cea607c767d42b1b..334d3832357bb08d2d2836e36781b44c3585cb8a 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc
@@ -18,7 +18,9 @@ namespace blink {
 NGBlockLayoutAlgorithm::NGBlockLayoutAlgorithm(
     PassRefPtr<const ComputedStyle> style,
     NGBox* first_child)
-    : style_(style), first_child_(first_child), state_(kStateInit) {}
+    : style_(style), first_child_(first_child), state_(kStateInit) {
+  DCHECK(style_);
+}
 
 bool NGBlockLayoutAlgorithm::Layout(const NGConstraintSpace* constraint_space,
                                     NGPhysicalFragment** out) {