Let the browser know about the renderer's page id assignments, even if the renderer is swapped out.

content/common/swapped_out_messages.cc

Index: content/common/swapped_out_messages.cc
diff --git a/content/common/swapped_out_messages.cc b/content/common/swapped_out_messages.cc
index a639a7ee4bac42056459d8908bda2bbac4efcd37..6c872d43f1aa33661262edb7c5ea6fcb9188d03f 100644
--- a/content/common/swapped_out_messages.cc
+++ b/content/common/swapped_out_messages.cc
@@ -44,6 +44,9 @@ bool SwappedOutMessages::CanSendWhileSwappedOut(const IPC::Message* msg) {
     // Input events propagate from parent to child.
     case FrameHostMsg_ForwardInputEvent::ID:
     case FrameHostMsg_InitializeChildFrame::ID:
+    // The browser should always have an accurate mirror of the renderer's
+    // notion of the current page id.
+    case FrameHostMsg_DidAssignPageId::ID:
       return true;
     default:
       break;