Convert PlatformVerificationDialog to use the new navigation callbacks.

chrome/browser/chromeos/attestation/platform_verification_dialog.h

Index: chrome/browser/chromeos/attestation/platform_verification_dialog.h
diff --git a/chrome/browser/chromeos/attestation/platform_verification_dialog.h b/chrome/browser/chromeos/attestation/platform_verification_dialog.h
index 9e271fe131104b55b1f1b9f204e9eb5c11597a51..87f350f1535b95ef5ab049606953026749197bcb 100644
--- a/chrome/browser/chromeos/attestation/platform_verification_dialog.h
+++ b/chrome/browser/chromeos/attestation/platform_verification_dialog.h
@@ -67,9 +67,8 @@ class PlatformVerificationDialog : public views::DialogDelegateView,
                               int event_flags) override;
 
   // content::WebContentsObserver:
-  void DidStartNavigationToPendingEntry(
-      const GURL& url,
-      content::ReloadType reload_type) override;
+  void DidStartNavigation(
+      content::NavigationHandle* navigation_handle) override;
 
   base::string16 domain_;
   ConsentCallback callback_;