Add pending preloads indexed by routing id. Start preloading once we navigate.

chrome/browser/prerender/prerender_contents.cc

Index: chrome/browser/prerender/prerender_contents.cc
diff --git a/chrome/browser/prerender/prerender_contents.cc b/chrome/browser/prerender/prerender_contents.cc
index 5313cf0503289e154957c57a31a83ba44be6018f..078d3d5d462ebe628378fd7f15106954c2694372 100644
--- a/chrome/browser/prerender/prerender_contents.cc
+++ b/chrome/browser/prerender/prerender_contents.cc
@@ -143,6 +143,24 @@ void PrerenderContents::StartPrerendering() {
   render_view_host_->Navigate(params);
 }
 
+bool PrerenderContents::child_id(int* child_id) const {
+  CHECK(child_id);
+  if (render_view_host_) {
+    *child_id = render_view_host_->process()->id();
+    return true;
+  }
+  return false;
+}
+
+bool PrerenderContents::route_id(int* route_id) const {
+  CHECK(route_id);
+  if (render_view_host_) {
+    *route_id = render_view_host_->routing_id();
+    return true;
+  }
+  return false;
+}
+
 void PrerenderContents::set_final_status(FinalStatus final_status) {
   DCHECK(final_status >= FINAL_STATUS_USED && final_status < FINAL_STATUS_MAX);
   DCHECK_EQ(FINAL_STATUS_MAX, final_status_);