Don't try to access the plugin_ after we deleted in the in plugin placeholder

components/plugins/renderer/plugin_placeholder.cc

 // Copyright 2013 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 "components/plugins/renderer/plugin_placeholder.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/json/string_escape.h"
 #include "base/strings/string_piece.h"
@@ skipping 89 matching lines @@
   plugin_->RestoreTitleText();
   container->invalidate();
   container->reportGeometry();
   plugin_->ReplayReceivedData(new_plugin);
   plugin_->destroy();
   plugin_ = NULL;
 }
 
 void PluginPlaceholder::HidePlugin() {
   hidden_ = true;
+  if (!plugin_)
+    return;
   WebPluginContainer* container = plugin_->container();
   WebElement element = container->element();
   element.setAttribute("style", "display: none;");
   // If we have a width and height, search for a parent (often <div>) with the
   // same dimensions. If we find such a parent, hide that as well.
   // This makes much more uncovered page content usable (including clickable)
   // as opposed to merely visible.
   // TODO(cevans) -- it's a foul heurisitc but we're going to tolerate it for
   // now for these reasons:
   // 1) Makes the user experience better.
@@ skipping 31 matching lines @@
   }
 }
 
 void PluginPlaceholder::SetMessage(const base::string16& message) {
   message_ = message;
   if (finished_loading_)
     UpdateMessage();
 }
 
 void PluginPlaceholder::UpdateMessage() {
+  if (!plugin_)
+    return;
   std::string script =
       "window.setMessage(" + base::GetQuotedJSONString(message_) + ")";
   plugin_->web_view()->mainFrame()->executeScript(
       WebScriptSource(base::ASCIIToUTF16(script)));
 }
 
 void PluginPlaceholder::ShowContextMenu(const WebMouseEvent& event) {
   // Does nothing by default. Will be overridden if a specific browser wants
   // a context menu.
   return;
@@ skipping 66 matching lines @@
   identifier_ = identifier;
 }
 
 blink::WebFrame* PluginPlaceholder::GetFrame() { return frame_; }
 
 const blink::WebPluginParams& PluginPlaceholder::GetPluginParams() const {
   return plugin_params_;
 }
 
 }  // namespace plugins