Use InterstitialPage through a delegate interface instead of deriving from it.

chrome/browser/safe_browsing/safe_browsing_blocking_page_test.cc

Index: chrome/browser/safe_browsing/safe_browsing_blocking_page_test.cc
===================================================================
--- chrome/browser/safe_browsing/safe_browsing_blocking_page_test.cc	(revision 120576)
+++ chrome/browser/safe_browsing/safe_browsing_blocking_page_test.cc	(working copy)
@@ -21,6 +21,7 @@
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "content/browser/renderer_host/resource_dispatcher_host.h"
+#include "content/browser/tab_contents/interstitial_page.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_view.h"
@@ -264,21 +265,22 @@
     service->AddURLResult(url, checkresult);
   }
 
-  void SendCommand(const std::string& command) {
-    WebContents* contents =
-        browser()->GetSelectedTabContentsWrapper()->web_contents();
+  TestSafeBrowsingBlockingPage* GetSafeBrowsingBlockingPage() {
     // We use InterstitialPage::GetInterstitialPage(tab) instead of
     // tab->GetInterstitialPage() because the tab doesn't have a pointer
     // to its interstital page until it gets a command from the renderer
     // that it has indeed displayed it -- and this sometimes happens after
     // NavigateToURL returns.
-    SafeBrowsingBlockingPage* interstitial_page =
-        static_cast<SafeBrowsingBlockingPage*>(
-            InterstitialPage::GetInterstitialPage(contents));
-    ASSERT_TRUE(interstitial_page);
-    interstitial_page->CommandReceived(command);
+    WebContents* contents =
+        browser()->GetSelectedTabContentsWrapper()->web_contents();
+    return static_cast<TestSafeBrowsingBlockingPage*>(
+          contents->GetInterstitialPage()->GetDelegateForTesting());
   }
 
+  void SendCommand(const std::string& command) {
+    GetSafeBrowsingBlockingPage()->CommandReceived(command);
+  }
+
   void DontProceedThroughInterstitial() {
     WebContents* contents =
         browser()->GetSelectedTabContentsWrapper()->web_contents();
@@ -303,8 +305,7 @@
 
     if (contents->ShowingInterstitialPage() && wait_for_delete) {
       // We'll get notified when the interstitial is deleted.
-      static_cast<TestSafeBrowsingBlockingPage*>(
-          contents->GetInterstitialPage())->set_wait_for_delete();
+      GetSafeBrowsingBlockingPage()->set_wait_for_delete();
       ui_test_utils::RunMessageLoop();
     }