RenderWidgetHostView: Fix a crash that occurrs when the TabContents is being

content/browser/renderer_host/render_widget_host_view_win.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 "content/browser/renderer_host/render_widget_host_view_win.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/i18n/rtl.h"
@@ skipping 313 matching lines @@
 }
 
 void RenderWidgetHostViewWin::DidBecomeSelected() {
   if (!is_hidden_)
     return;
 
   if (tab_switch_paint_time_.is_null())
     tab_switch_paint_time_ = TimeTicks::Now();
   is_hidden_ = false;
   EnsureTooltip();
-  render_widget_host_->WasRestored();
+
+  // |render_widget_host_| may be NULL if the TabContents is in the process of
+  // closing.
+  if (render_widget_host_)
+    render_widget_host_->WasRestored();
 }
 
 void RenderWidgetHostViewWin::WasHidden() {
   if (is_hidden_)
     return;
 
   // If we receive any more paint messages while we are hidden, we want to
   // ignore them so we don't re-allocate the backing store.  We will paint
   // everything again when we become selected again.
   is_hidden_ = true;
@@ skipping 1669 matching lines @@
 
   if (message == WM_MOUSEMOVE) {
     CPoint center = GetClientCenter();
     // Ignore WM_MOUSEMOVE messages generated by MoveCursorToCenter().
     if (LOWORD(lparam) == center.x && HIWORD(lparam) == center.y)
       return;
   }
 
   ForwardMouseEventToRenderer(message, wparam, lparam);
 }