Add WaitForInterstitialReady to browser_test_utils.

chrome/browser/safe_browsing/safe_browsing_blocking_page.cc

Index: chrome/browser/safe_browsing/safe_browsing_blocking_page.cc
diff --git a/chrome/browser/safe_browsing/safe_browsing_blocking_page.cc b/chrome/browser/safe_browsing/safe_browsing_blocking_page.cc
index 5b053b1ca040de77a95d57ccc3c5ad277c54bbda..0515ecd840fd7f5bc6a071cc32795f5bb1f5f1f1 100644
--- a/chrome/browser/safe_browsing/safe_browsing_blocking_page.cc
+++ b/chrome/browser/safe_browsing/safe_browsing_blocking_page.cc
@@ -220,6 +220,13 @@ void SafeBrowsingBlockingPage::CommandReceived(const std::string& cmd) {
   if (command.length() > 1 && command[0] == '"') {
     command = command.substr(1, command.length() - 2);
   }
+
+  if (command == "pageLoadComplete") {
+    // content::WaitForRenderFrameReady sends this message when the page
+    // load completes. Ignore it.
+    return;
+  }
+
   if (command == kDoReportCommand) {
     SetReportingPreference(true);
     return;