Add ShowLayoutOpportunityTree to NGLayoutOpportunityIterator

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

Index: third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_iterator.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_iterator.cc b/third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_iterator.cc
index ac2930618bc1d1910990bc6705fbb430d7650ae1..f95d51d176ef7445381c363cce38b3fa787a9741 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_iterator.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_iterator.cc
@@ -7,10 +7,41 @@
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_exclusion.h"
 #include "wtf/NonCopyingSort.h"
+#include "wtf/text/StringBuilder.h"
 
 namespace blink {
 namespace {
 
+void AppendNodeToString(const NGLayoutOpportunityTreeNode* node,
+                        StringBuilder* string_builder,
+                        unsigned indent = 0) {
+  DCHECK(string_builder);
+  if (!node) {
+    string_builder->append("'null'\n");
+    return;
+  }
+
+  string_builder->append(node->ToString());
+  string_builder->append("\n");
+
+  StringBuilder indent_builder;
+  for (unsigned i = 0; i < indent; i++)
+    indent_builder.append("\t");
+
+  if (!node->exclusion)
+    return;
+
+  string_builder->append(indent_builder.toString());
+  string_builder->append("Left:\t");
+  AppendNodeToString(node->left, string_builder, indent + 2);
+  string_builder->append(indent_builder.toString());
+  string_builder->append("Right:\t");
+  AppendNodeToString(node->right, string_builder, indent + 2);
+  string_builder->append(indent_builder.toString());
+  string_builder->append("Bottom:\t");
+  AppendNodeToString(node->bottom, string_builder, indent + 2);
+}
+
 // Collects all opportunities from leaves of Layout Opportunity spatial tree.
 void CollectAllOpportunities(const NGLayoutOpportunityTreeNode* node,
                              NGLayoutOpportunities& opportunities) {
@@ -276,4 +307,13 @@ const NGLayoutOpportunity NGLayoutOpportunityIterator::Next() {
   return NGLayoutOpportunity(*opportunity);
 }
 
+#ifndef NDEBUG
+void NGLayoutOpportunityIterator::ShowLayoutOpportunityTree() const {
+  StringBuilder string_builder;
+  string_builder.append("\n.:: LayoutOpportunity Tree ::.\n\nRoot Node: ");
+  AppendNodeToString(opportunity_tree_root_.get(), &string_builder);
+  fprintf(stderr, "%s\n", string_builder.toString().utf8().data());
+}
+#endif
+
 }  // namespace blink