Write a test for my previous patch to fix a crash in back/forward navigations...

chrome/test/browser_with_test_window_test.cc

Index: chrome/test/browser_with_test_window_test.cc
===================================================================
--- chrome/test/browser_with_test_window_test.cc	(revision 14577)
+++ chrome/test/browser_with_test_window_test.cc	(working copy)
@@ -5,6 +5,7 @@
 #include "chrome/test/browser_with_test_window_test.h"
 
 #include "chrome/browser/browser.h"
+#include "chrome/browser/tab_contents/navigation_entry.h"
 #include "chrome/common/render_messages.h"
 #include "chrome/test/test_browser_window.h"
 #include "chrome/test/testing_profile.h"
@@ -51,25 +52,37 @@
   TabContents* new_tab = browser->AddTabWithURL(url, GURL(),
                                                 PageTransition::TYPED, true,
                                                 0, NULL);
-  CommitPendingLoadAsNewNavigation(&new_tab->controller(), url);
+  CommitPendingLoad(&new_tab->controller());
 }
 
-void BrowserWithTestWindowTest::CommitPendingLoadAsNewNavigation(
-    NavigationController* controller,
-    const GURL& url) {
+void BrowserWithTestWindowTest::CommitPendingLoad(
+    NavigationController* controller) {
+  if (!controller->pending_entry())
+    return;  // Nothing to commit.
+
   TestRenderViewHost* test_rvh =
       TestRenderViewHostForTab(controller->tab_contents());
   MockRenderProcessHost* mock_rph = static_cast<MockRenderProcessHost*>(
     test_rvh->process());
 
-  test_rvh->SendNavigate(mock_rph->max_page_id() + 1, url);
+  // For new navigations, we need to send a larger page ID. For renavigations,
+  // we need to send the preexisting page ID. We can tell these apart because
+  // renavigations will have a pending_entry_index while new ones won't (they'll
+  // just have a standalong pending_entry that isn't in the list already).
+  if (controller->pending_entry_index() >= 0) {
+    test_rvh->SendNavigate(controller->pending_entry()->page_id(),
+                           controller->pending_entry()->url());
+  } else {
+    test_rvh->SendNavigate(mock_rph->max_page_id() + 1,
+                           controller->pending_entry()->url());
+  }
 }
 
 void BrowserWithTestWindowTest::NavigateAndCommit(
     NavigationController* controller,
     const GURL& url) {
   controller->LoadURL(url, GURL(), 0);
-  CommitPendingLoadAsNewNavigation(controller, url);
+  CommitPendingLoad(controller);
 }
 
 void BrowserWithTestWindowTest::NavigateAndCommitActiveTab(const GURL& url) {