GTK: add more syncronization to GtkNativeViewIdManager to avoid a crash.

gfx/gtk_native_view_id_manager.h

 // Copyright (c) 2009 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.
 
 #ifndef GFX_GTK_NATIVE_VIEW_ID_MANAGER_H_
 #define GFX_GTK_NATIVE_VIEW_ID_MANAGER_H_
 
 #include <map>
 
 #include "base/singleton.h"
@@ skipping 45 matching lines @@
   //
   // If the widget referenced by |id| does not current have an X window id,
   // |*xid| is set to 0.
   bool GetXIDForId(XID* xid, gfx::NativeViewId id);
 
   // These are actually private functions, but need to be called from statics.
   void OnRealize(gfx::NativeView widget);
   void OnUnrealize(gfx::NativeView widget);
   void OnDestroy(gfx::NativeView widget);
 
+  Lock& unrealize_lock() { return unrealize_lock_; }
+
  private:
   // This object is a singleton:
   GtkNativeViewManager();
   friend struct DefaultSingletonTraits<GtkNativeViewManager>;
 
   struct NativeViewInfo {
     NativeViewInfo()
         : x_window_id(0) {
     }
 
     XID x_window_id;
   };
 
   gfx::NativeViewId GetWidgetId(gfx::NativeView id);
 
+  // This lock can be used to block GTK from unrealizing windows. This is needed
+  // when the BACKGROUND_X11 thread is using a window obtained via GetXIDForId,
+  // and can't allow the X11 resource to be deleted.
+  Lock unrealize_lock_;
+
   // protects native_view_to_id_ and id_to_info_
   Lock lock_;
-    // If asked for an id for the same widget twice, we want to return the same
-    // id. So this records the current mapping.
-    std::map<gfx::NativeView, gfx::NativeViewId> native_view_to_id_;
-    std::map<gfx::NativeViewId, NativeViewInfo> id_to_info_;
+
+  // If asked for an id for the same widget twice, we want to return the same
+  // id. So this records the current mapping.
+  std::map<gfx::NativeView, gfx::NativeViewId> native_view_to_id_;
+  std::map<gfx::NativeViewId, NativeViewInfo> id_to_info_;
 
   DISALLOW_COPY_AND_ASSIGN(GtkNativeViewManager);
 };
 
 #endif  // GFX_GTK_NATIVE_VIEW_ID_MANAGER_H_