Temporarily dump without crashing when setting an empty PageState.

content/browser/frame_host/frame_navigation_entry.cc

Index: content/browser/frame_host/frame_navigation_entry.cc
diff --git a/content/browser/frame_host/frame_navigation_entry.cc b/content/browser/frame_host/frame_navigation_entry.cc
index 26671f7df448e60a5c8fc0cf5bd8aa7927f11cb5..d28a80f18173e69c263d6f922ca65ceb6aace3a2 100644
--- a/content/browser/frame_host/frame_navigation_entry.cc
+++ b/content/browser/frame_host/frame_navigation_entry.cc
@@ -6,6 +6,7 @@
 
 #include <utility>
 
+#include "base/debug/dump_without_crashing.h"
 #include "content/common/page_state_serialization.h"
 #include "content/common/site_isolation_policy.h"
 
@@ -65,6 +66,11 @@ void FrameNavigationEntry::UpdateEntry(
   source_site_instance_ = std::move(source_site_instance);
   url_ = url;
   referrer_ = referrer;
+  if (!page_state.IsValid()) {
+    // Temporarily generate a minidump to diagnose https://crbug.com/568703.
+    base::debug::DumpWithoutCrashing();
+    NOTREACHED() << "Shouldn't set an empty PageState.";
+  }
   page_state_ = page_state;
   method_ = method;
   post_id_ = post_id;