Fix unload controller.

chrome/browser/ui/unload_controller.cc

Index: chrome/browser/ui/unload_controller.cc
diff --git a/chrome/browser/ui/unload_controller.cc b/chrome/browser/ui/unload_controller.cc
index 8da59883131c958fbd7a16fe9daa400225b43eb7..7a30244ff82a5b5d2a596bc747714e12bc18e913 100644
--- a/chrome/browser/ui/unload_controller.cc
+++ b/chrome/browser/ui/unload_controller.cc
@@ -291,6 +291,9 @@ void UnloadController::TabDetachedImpl(content::WebContents* contents) {
 }
 
 void UnloadController::ProcessPendingTabs() {
+  // Cancel posted/queued ProcessPendingTabs task if there is any.
+  weak_factory_.InvalidateWeakPtrs();
+
   if (!is_attempting_to_close_browser_) {
     // Because we might invoke this after a delay it's possible for the value of
     // is_attempting_to_close_browser_ to have changed since we scheduled the
@@ -298,7 +301,7 @@ void UnloadController::ProcessPendingTabs() {
     return;
   }
 
-  if (HasCompletedUnloadProcessing()) {
+  if (HasCompletedUnloadProcessing() && !TabsNeedBeforeUnloadFired()) {

[sky, 2017/02/16 17:16:53]

How come we don't always call TabsNeedBeforeUnloadFired?

[Michael K. (Yandex Team), 2017/02/17 09:43:04]

We do. We always call it.
But since we called it and then called all beforeunload handlers (and
HasCompletedUnloadProcessing() == true) situation could change: there could
appear new beforeunload handler(s) that we hadn't known about.
Thus when we think we are done we should check it again: call
TabsNeedBeforeUnloadFired and know whether situation has changed or not.
 

     // We've finished all the unload events and can proceed to close the
     // browser.
     browser_->OnWindowClosing();
@@ -379,6 +382,9 @@ void UnloadController::ClearUnloadState(content::WebContents* web_contents,
     if (process_now) {
       ProcessPendingTabs();
     } else {
+      // Do not post a new task if there is already any.
+      if (weak_factory_.HasWeakPtrs())
+        return;
       base::ThreadTaskRunnerHandle::Get()->PostTask(
           FROM_HERE, base::Bind(&UnloadController::ProcessPendingTabs,
                                 weak_factory_.GetWeakPtr()));