Make base::Value::TYPE a scoped enum.

tools/gn/command_desc.cc

Index: tools/gn/command_desc.cc
diff --git a/tools/gn/command_desc.cc b/tools/gn/command_desc.cc
index 9f7f903c986d2edb3ccb307a11b817d1f0f0aa98..1de9fbb12da098508eb2898209a7f4f4882e3855 100644
--- a/tools/gn/command_desc.cc
+++ b/tools/gn/command_desc.cc
@@ -56,7 +56,7 @@ void PrintValue(const base::Value* value, int indentLevel) {
       PrintValue(&iter.value(), indentLevel + 1);
       iter.Advance();
     }
-  } else if (value->IsType(base::Value::TYPE_NULL)) {
+  } else if (value->IsType(base::Value::Type::NONE)) {
     OutputString(indent + "<null>\n");
   }
 }