Keep track in the browser of which frames have onunload and onbeforeunload handlers.

chrome/browser/lifetime/browser_close_manager.cc

Index: chrome/browser/lifetime/browser_close_manager.cc
diff --git a/chrome/browser/lifetime/browser_close_manager.cc b/chrome/browser/lifetime/browser_close_manager.cc
index d8a943c1ab55a4172d9b0c66e9a8de2909183c1c..484a1f3bf0a4cc5dee0e90797e7bd4694e84b924 100644
--- a/chrome/browser/lifetime/browser_close_manager.cc
+++ b/chrome/browser/lifetime/browser_close_manager.cc
@@ -72,13 +72,16 @@ void BrowserCloseManager::TryToCloseBrowsers() {
   // OnBrowserReportCloseable with the result. If the user confirms the close,
   // this will trigger TryToCloseBrowsers to try again.
   for (auto* browser : *BrowserList::GetInstance()) {
+    // Set current_browser_ here since if there are no unload handlers, it might
+    // get used synchronously inside TryToCloseWindow.
+    current_browser_ = browser;
     if (browser->TryToCloseWindow(
             false,
             base::Bind(&BrowserCloseManager::OnBrowserReportCloseable, this))) {
-      current_browser_ = browser;
       return;
     }
   }
+  current_browser_ = NULL;
   CheckForDownloadsInProgress();
 }