Add WaitForInterstitialReady to browser_test_utils.

content/public/test/browser_test_utils.cc

Index: content/public/test/browser_test_utils.cc
diff --git a/content/public/test/browser_test_utils.cc b/content/public/test/browser_test_utils.cc
index 89dd3430e96dbca0330338b1fc035951d215e908..52f5fd72a62f96608beef9fe63b6c6e4d7c66a95 100644
--- a/content/public/test/browser_test_utils.cc
+++ b/content/public/test/browser_test_utils.cc
@@ -21,6 +21,7 @@
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/dom_operation_notification_details.h"
 #include "content/public/browser/histogram_fetcher.h"
+#include "content/public/browser/interstitial_page.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_types.h"
@@ -723,6 +724,29 @@ void RunTaskAndWaitForInterstitialDetach(content::WebContents* web_contents,
   loop_runner->Run();
 }
 
+bool WaitForInterstitialReady(content::InterstitialPage* interstitial) {
+  content::RenderFrameHost* rfh = interstitial->GetMainFrame();

[mattm, 2015/01/22 02:28:32]

Since the rest of this function isn't interstitial specific, would it be useful
to just take a RenderFrameHost and call it WaitForRenderFrameReady or something
like that?

[meacer, 2015/01/22 03:18:07]

Done.

+  if (!rfh)
+    return false;
+  bool load_complete = false;
+  EXPECT_TRUE(
+      content::ExecuteScriptAndExtractBool(
+          rfh,
+          "(function() {"
+          "  var done = false;"
+          "  function checkState() {"
+          "    if (!done && document.readyState == 'complete') {"
+          "      done = true;"
+          "      window.domAutomationController.send(true);"
+          "    }"
+          "  }"
+          "  checkState();"
+          "  document.addEventListener('readystatechange', checkState);"
+          "})();",
+          &load_complete));
+  return load_complete;
+}
+
 TitleWatcher::TitleWatcher(WebContents* web_contents,
                            const base::string16& expected_title)
     : WebContentsObserver(web_contents),