Add a second line of defense for receiving a bad message in the renderer.

content/browser/tab_contents/tab_contents.cc

Index: content/browser/tab_contents/tab_contents.cc
diff --git a/content/browser/tab_contents/tab_contents.cc b/content/browser/tab_contents/tab_contents.cc
index d4d1ccbf1655dbbcc5c47eb314ecd33d05ba2648..c451cc96d8719564b5ec5415426f17ed45cb0cc4 100644
--- a/content/browser/tab_contents/tab_contents.cc
+++ b/content/browser/tab_contents/tab_contents.cc
@@ -573,15 +573,15 @@ bool TabContents::NavigateToPendingEntry(
 bool TabContents::NavigateToEntry(
     const NavigationEntry& entry,
     NavigationController::ReloadType reload_type) {
-  RenderViewHost* dest_render_view_host = render_manager_.Navigate(entry);
-  if (!dest_render_view_host)
-    return false;  // Unable to create the desired render view host.
-
   // The renderer will reject IPC messages with URLs longer than
   // this limit, so don't attempt to navigate with a longer URL.
   if (entry.url().spec().size() > content::kMaxURLChars)
     return false;
 
+  RenderViewHost* dest_render_view_host = render_manager_.Navigate(entry);
+  if (!dest_render_view_host)
+    return false;  // Unable to create the desired render view host.
+
   // For security, we should never send non-Web-UI URLs to a Web UI renderer.
   // Double check that here.
   int enabled_bindings = dest_render_view_host->enabled_bindings();