Added support for (de)serializing cc::RendererSettings

As part of serializing cc::LayerTreeHost, we also need to
serialize the cc::LayerTreeSettings and the cc::RendererSettings.

This CL focuses only on the renderer settings.

BUG=561210
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1476753002

Cr-Commit-Position: refs/heads/master@{#362558}

diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index 2b24a2c..c0253ab 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn

@@ -805,6 +805,7 @@
     "output/output_surface_unittest.cc",
     "output/overlay_unittest.cc",
     "output/renderer_pixeltest.cc",
+    "output/renderer_settings_unittest.cc",
     "output/renderer_unittest.cc",
     "output/shader_unittest.cc",
     "output/software_renderer_unittest.cc",