add --enable-spatial-navigation flag for testing

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index dd65920040aa2411578cc068a05760086b40b9a4..ac80a96054eab76ca4f2eaf8fce86472b33d8690 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -597,6 +597,9 @@ WebPreferences WebContentsImpl::GetWebkitPrefs(RenderViewHost* rvh,
       command_line.HasSwitch(switches::kEnableDeferredImageDecoding) ||
       cc::switches::IsImplSidePaintingEnabled();
 
+  prefs.spatial_navigation_enabled = command_line.HasSwitch(
+      switches::kEnableSpatialNavigation);
+
   GetContentClient()->browser()->OverrideWebkitPrefs(rvh, url, &prefs);
 
   // Disable compositing in guests until we have compositing path implemented