PlzNavigate: implement RequestNavigation in the no live renderer case

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index db429e3c852ccc9ae72d6daf97159eef34415154..a1676d14071475b0d0a871af448a74606f4657b8 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -320,6 +320,9 @@ const char kEnableContainerCulling[]        = "enable-container-culling";
 // Use a BeginFrame signal from browser to renderer to schedule rendering.
 const char kEnableBeginFrameScheduling[]    = "enable-begin-frame-scheduling";
 
+// Use the experimental browser-side navigation path (PlzNavigate project).
+const char kEnableBrowserSideNavigation[]   = "enable-browser-side-navigation";
+
 // Enable the creation of compositing layers for fixed position
 // elements. Three options are needed to support four possible scenarios:
 //  1. Default (disabled)