[Extensions Bindings] Fix uninitialized member in ArgumentSpec

extensions/renderer/argument_spec.h

Index: extensions/renderer/argument_spec.h
diff --git a/extensions/renderer/argument_spec.h b/extensions/renderer/argument_spec.h
index 4c85858326b5f19f879e7a1bc4313d232ba0f3b5..84e27731c68bfce5923addb0c87c882465945fe8 100644
--- a/extensions/renderer/argument_spec.h
+++ b/extensions/renderer/argument_spec.h
@@ -121,13 +121,13 @@ class ArgumentSpec {
   std::string name_;
 
   // The type of the argument.
-  ArgumentType type_;
+  ArgumentType type_ = ArgumentType::INTEGER;
 
   // Whether or not the argument is required.
-  bool optional_;
+  bool optional_ = false;
 
   // Whether to preserve null properties found in objects.
-  bool preserve_null_;
+  bool preserve_null_ = false;
 
   // The reference the argument points to, if any. Note that if this is set,
   // none of the following fields describing the argument will be.