[Prerender] Change IPC from bool to enum for more prerender modes

chrome/renderer/chrome_render_frame_observer.cc

Index: chrome/renderer/chrome_render_frame_observer.cc
diff --git a/chrome/renderer/chrome_render_frame_observer.cc b/chrome/renderer/chrome_render_frame_observer.cc
index 54fb694165bd617f0d67798d6f16cad36c4ee3aa..acf3f2c9950d54e915cbd9bf2b4888665ba924e7 100644
--- a/chrome/renderer/chrome_render_frame_observer.cc
+++ b/chrome/renderer/chrome_render_frame_observer.cc
@@ -158,8 +158,9 @@ bool ChromeRenderFrameObserver::OnMessageReceived(const IPC::Message& message) {
   return handled;
 }
 
-void ChromeRenderFrameObserver::OnSetIsPrerendering(bool is_prerendering) {
-  if (is_prerendering) {
+void ChromeRenderFrameObserver::OnSetIsPrerendering(
+    prerender::PrerenderMode mode) {
+  if (mode != prerender::NO_PRERENDER) {
     // If the PrerenderHelper for this frame already exists, don't create it. It
     // can already be created for subframes during handling of
     // RenderFrameCreated, if the parent frame was prerendering at time of