Support read-only duplicates of Mojo shared buffers.

mojo/edk/test/mojo_test_base.cc

Index: mojo/edk/test/mojo_test_base.cc
diff --git a/mojo/edk/test/mojo_test_base.cc b/mojo/edk/test/mojo_test_base.cc
index 4b044f6334c9f0c1709738516e07c1b1c39f1e82..b9b68604ca155190771e0cb163b2c892836a82fe 100644
--- a/mojo/edk/test/mojo_test_base.cc
+++ b/mojo/edk/test/mojo_test_base.cc
@@ -224,10 +224,16 @@ MojoHandle MojoTestBase::CreateBuffer(uint64_t size) {
 }
 
 // static
-MojoHandle MojoTestBase::DuplicateBuffer(MojoHandle h) {
+MojoHandle MojoTestBase::DuplicateBuffer(MojoHandle h, bool read_only) {
   MojoHandle new_handle;
+  MojoDuplicateBufferHandleOptions options = {
+    sizeof(MojoDuplicateBufferHandleOptions),
+    MOJO_DUPLICATE_BUFFER_HANDLE_OPTIONS_FLAG_NONE
+  };
+  if (read_only)
+    options.flags |= MOJO_DUPLICATE_BUFFER_HANDLE_OPTIONS_FLAG_READ_ONLY;
   EXPECT_EQ(MOJO_RESULT_OK,
-            MojoDuplicateBufferHandle(h, nullptr, &new_handle));
+            MojoDuplicateBufferHandle(h, &options, &new_handle));
   return new_handle;
 }