Revert of Address a crash under -[NSWindow close] via a WeakPtr PostTask from Browser::TabStripEmpty

chrome/browser/ui/cocoa/browser_window_cocoa.mm

Index: chrome/browser/ui/cocoa/browser_window_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/browser_window_cocoa.mm b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
index 8a26e926bbe3f41c2f25f4452ed50cadff92df26..11b6485b8c278c6ea9ee7723dd62f2a305bc0a3e 100644
--- a/chrome/browser/ui/cocoa/browser_window_cocoa.mm
+++ b/chrome/browser/ui/cocoa/browser_window_cocoa.mm
@@ -132,12 +132,11 @@
 
 BrowserWindowCocoa::BrowserWindowCocoa(Browser* browser,
                                        BrowserWindowController* controller)
-    : browser_(browser),
-      controller_(controller),
-      initial_show_state_(ui::SHOW_STATE_DEFAULT),
-      attention_request_id_(0),
-      alert_state_(TabAlertState::NONE),
-      window_closed_(false) {
+  : browser_(browser),
+    controller_(controller),
+    initial_show_state_(ui::SHOW_STATE_DEFAULT),
+    attention_request_id_(0) {
+
   gfx::Rect bounds;
   chrome::GetSavedWindowBoundsAndShowState(browser_,
                                            &bounds,
@@ -762,9 +761,10 @@
 
 web_modal::WebContentsModalDialogHost*
     BrowserWindowCocoa::GetWebContentsModalDialogHost() {
-  DCHECK(window());
+  DCHECK([controller_ window]);
   ConstrainedWindowSheetController* sheet_controller =
-      [ConstrainedWindowSheetController controllerForParentWindow:window()];
+      [ConstrainedWindowSheetController
+          controllerForParentWindow:[controller_ window]];
   DCHECK(sheet_controller);
   return [sheet_controller dialogHost];
 }
@@ -792,12 +792,6 @@
 }
 
 NSWindow* BrowserWindowCocoa::window() const {
-  // AppKit doesn't seem to guarantee that [controller_ window] returns nil once
-  // the NSWindow is destroyed. Since |this| is deleted only once
-  // -[NSWindowController dealloc] completes, there's a possibility of
-  // a WeakPtr to Browser* requesting the NSWindow, which may be a zombie.
-  if (window_closed_)
-    return nil;
   return [controller_ window];
 }
 
@@ -847,7 +841,3 @@
         callback) {
   NOTREACHED() << "The IME warning bubble is unsupported on this platform.";
 }
-
-void BrowserWindowCocoa::OnWindowWillClose() {
-  window_closed_ = true;
-}