Mojo: Use new message APIs to reduce copying

mojo/public/cpp/system/handle.h

Index: mojo/public/cpp/system/handle.h
diff --git a/mojo/public/cpp/system/handle.h b/mojo/public/cpp/system/handle.h
index 519bcc1ea88a01f20c2c2dd8673d194b47d4f0ec..f83a9226f1891e2904341f54d01c75d32bfb8678 100644
--- a/mojo/public/cpp/system/handle.h
+++ b/mojo/public/cpp/system/handle.h
@@ -124,11 +124,8 @@ class ScopedHandleBase {
 
  private:
   void CloseIfNecessary() {
-    if (!handle_.is_valid())
-      return;
-    MojoResult result = MojoClose(handle_.value());
-    ALLOW_UNUSED_LOCAL(result);
-    DCHECK_EQ(MOJO_RESULT_OK, result);
+    if (handle_.is_valid())
+      handle_.Close();
   }
 
   HandleType handle_;
@@ -162,6 +159,13 @@ class Handle {
   MojoHandle* mutable_value() { return &value_; }
   void set_value(MojoHandle value) { value_ = value; }
 
+  void Close() {
+    DCHECK(is_valid());
+    MojoResult result = MojoClose(value_);
+    ALLOW_UNUSED_LOCAL(result);
+    DCHECK_EQ(MOJO_RESULT_OK, result);
+  }
+
  private:
   MojoHandle value_;