Mojo: Make default Options directly accessible.

mojo/system/data_pipe.h

Index: mojo/system/data_pipe.h
diff --git a/mojo/system/data_pipe.h b/mojo/system/data_pipe.h
index c4e0d781cb8a3ea3b041e2b4bd02dbfa50c93142..d544f878f05c046e3eed7546afaaae47120279af 100644
--- a/mojo/system/data_pipe.h
+++ b/mojo/system/data_pipe.h
@@ -28,6 +28,12 @@ class WaiterList;
 class MOJO_SYSTEM_IMPL_EXPORT DataPipe :
     public base::RefCountedThreadSafe<DataPipe> {
  public:
+  // The default options to use for the constructor (and subclasses'
+  // constructors). (Real uses should obtain this via |ValidateCreateOptions()|
+  // with a null |in_options|; this is exposed directly for testing
+  // convenience.)
+  static const MojoCreateDataPipeOptions kDefaultCreateOptions;
+
   // Validates and/or sets default options for |MojoCreateDataPipeOptions|. If
   // non-null, |in_options| must point to a struct of at least
   // |in_options->struct_size| bytes. |out_options| must point to a (current)