EDK: Add implementation of data pipe producer write threshold stuff.

mojo/edk/system/data_pipe_impl.h

Index: mojo/edk/system/data_pipe_impl.h
diff --git a/mojo/edk/system/data_pipe_impl.h b/mojo/edk/system/data_pipe_impl.h
index e92d66cc1a8f1cbc7c5439fea0a44a21de662137..bd3cc3164d40e598a879670bdd4ead09c2a8b8e3 100644
--- a/mojo/edk/system/data_pipe_impl.h
+++ b/mojo/edk/system/data_pipe_impl.h
@@ -144,6 +144,10 @@ class DataPipeImpl {
   bool consumer_open() const MOJO_NO_THREAD_SAFETY_ANALYSIS {
     return owner_->consumer_open_no_lock();
   }
+  size_t producer_write_threshold_num_bytes() const
+      MOJO_NO_THREAD_SAFETY_ANALYSIS {
+    return owner_->producer_write_threshold_num_bytes_no_lock();
+  }
   size_t consumer_read_threshold_num_bytes() const
       MOJO_NO_THREAD_SAFETY_ANALYSIS {
     return owner_->consumer_read_threshold_num_bytes_no_lock();