Don't display navigation error pages during layout tests

content/public/test/layouttest_support.h

Index: content/public/test/layouttest_support.h
diff --git a/content/public/test/layouttest_support.h b/content/public/test/layouttest_support.h
index a3f225ed3a608ef649eb2b39d5df77488c608064..fe623a0522259e91523d322051c8c9840f74fcc1 100644
--- a/content/public/test/layouttest_support.h
+++ b/content/public/test/layouttest_support.h
@@ -60,6 +60,9 @@ void EnableShortCircuitSizeUpdates();
 void ForceResizeRenderView(RenderView* render_view,
                            const WebKit::WebSize& new_size);
 
+// Never display error pages when a navigation fails.
+void DisableNavigationErrorPages();
+
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_TEST_LAYOUTTEST_SUPPORT_H_