Revert EnableClose() removal and related crash fixes. I don't understand the crashes here, and th...

chrome/browser/ui/views/frame/browser_non_client_frame_view_aura.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/views/frame/browser_non_client_frame_view_aura.h"
 
 #include "chrome/browser/ui/views/frame/browser_frame.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "grit/generated_resources.h"  // Accessibility names
 #include "grit/ui_resources.h"
@@ skipping 420 matching lines @@
 int BrowserNonClientFrameViewAura::NonClientHitTest(const gfx::Point& point) {
   last_hittest_code_ = NonClientHitTestImpl(point);
   return last_hittest_code_;
 }
 
 void BrowserNonClientFrameViewAura::GetWindowMask(const gfx::Size& size,
                                                   gfx::Path* window_mask) {
   // Nothing.
 }
 
+void BrowserNonClientFrameViewAura::EnableClose(bool enable) {
+  close_button_->SetEnabled(enable);
+}
+
 void BrowserNonClientFrameViewAura::ResetWindowControls() {
   maximize_button_->SetState(views::CustomButton::BS_NORMAL);
   // The close button isn't affected by this constraint.
 }
 
 void BrowserNonClientFrameViewAura::UpdateWindowIcon() {
   // TODO(jamescook): We will need this for app frames.
 }
 
 void BrowserNonClientFrameViewAura::ShouldPaintAsActiveChanged() {
@@ skipping 122 matching lines @@
 
 void BrowserNonClientFrameViewAura::OnWindowHoverChanged(bool hovered) {
   if (hovered) {
     maximize_button_->Show();
     close_button_->Show();
   } else {
     maximize_button_->Hide();
     close_button_->Hide();
   }
 }