Enable builtin Mojo JS modules in layout tests

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 84e6d1af9bb17da005014f5b438e4377adf6c9d2..6d1ad358a42b21c34c9d25e0823ff9b543d056f0 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -2359,8 +2359,14 @@ void RenderViewImpl::OnAllowBindings(int enabled_bindings_flags) {
       !(enabled_bindings_ & BINDINGS_POLICY_WEB_UI)) {
     // WebUIExtensionData deletes itself when we're destroyed.
     new WebUIExtensionData(this);
+  }
 
-    if (main_render_frame_)
+  if (main_render_frame_ &&
+      !(enabled_bindings_ & (BINDINGS_POLICY_WEB_UI | BINDINGS_POLICY_MOJO)) &&
+       (enabled_bindings_flags &
+            (BINDINGS_POLICY_WEB_UI | BINDINGS_POLICY_MOJO))) {
+      // Enable Mojo bindings iff either WebUI or Mojo bindings are being added
+      // to the policy and neither was present before.
       main_render_frame_->EnableMojoBindings();
   }