Implement lifetime observer on RenderWidgetHostViewBase.

content/browser/frame_host/render_widget_host_view_guest.cc

 // Copyright 2014 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/frame_host/render_widget_host_view_guest.h"
 
 #include <utility>
 
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
@@ skipping 523 matching lines @@
     gfx::NativeViewAccessible accessible_parent) {
 }
 
 gfx::NativeViewId RenderWidgetHostViewGuest::GetParentForWindowlessPlugin()
     const {
   return NULL;
 }
 #endif
 
 void RenderWidgetHostViewGuest::DestroyGuestView() {
-  UnregisterSurfaceNamespaceId();
+  // Let our observers know we're going away, since we don't want any event
+  // processing calls coming in after we release host_.
+  NotifyObserversAboutShutdown();
+
   host_->SetView(NULL);
   host_ = NULL;
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }
 
 RenderWidgetHostViewBase*
 RenderWidgetHostViewGuest::GetOwnerRenderWidgetHostView() const {
   return static_cast<RenderWidgetHostViewBase*>(
       guest_->GetOwnerRenderWidgetHostView());
 }
@@ skipping 85 matching lines @@
     if (gesture_event.type == blink::WebInputEvent::GestureScrollUpdate &&
         gesture_event.data.scrollUpdate.inertial) {
       return;
     }
     host_->ForwardGestureEvent(gesture_event);
     return;
   }
 }
 
 }  // namespace content