Remove unneeded AddRef in RenderViewTest::SetUp

The AddRef in RenderViewTest::SetUp is not needed and can lead to leaks
in tests. RenderView takes a reference on itself during initialization
and drops it in RenderWidget::Close (which it inherits & calls directly).

TBR=jam@chromium.org
BUG=357747

Review URL: https://codereview.chromium.org/1135643002

Cr-Commit-Position: refs/heads/master@{#328991}

content/public/test/render_view_test.cc

@@ -255,7 +255,6 @@ void RenderViewTest::SetUp() {
   // This needs to pass the mock render thread to the view.
   RenderViewImpl* view =
       RenderViewImpl::Create(view_params, compositor_deps_.get(), false);
-  view->AddRef();
   view_ = view;
 }