Plugin Power Saver: Fix race between GIN bindings and destruction

components/plugins/renderer/loadable_plugin_placeholder.cc

 // Copyright 2015 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/loadable_plugin_placeholder.h"
 
 #include <memory>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 312 matching lines @@
 
   // In case our initial geometry was reported before the placeholder finished
   // loading, request another one. Needed for correct large poster unthrottling.
   if (plugin()) {
     CHECK(plugin()->container());
     plugin()->container()->reportGeometry();
   }
 }
 
 void LoadablePluginPlaceholder::DidFinishIconRepositionForTestingCallback() {
+  if (!plugin())
+    return;
+
   // Set an attribute and post an event, so browser tests can wait for the
   // placeholder to be ready to receive simulated user input.
   blink::WebElement element = plugin()->container()->element();
   element.setAttribute("placeholderReady", "true");
 
   std::unique_ptr<content::V8ValueConverter> converter(
       content::V8ValueConverter::create());
   base::StringValue value("placeholderReady");
   blink::WebSerializedScriptValue message_data =
       blink::WebSerializedScriptValue::serialize(converter->ToV8Value(
@@ skipping 20 matching lines @@
   return identifier_;
 }
 
 bool LoadablePluginPlaceholder::LoadingBlocked() const {
   DCHECK(allow_loading_);
   return is_blocked_for_tinyness_ || is_blocked_for_background_tab_ ||
          is_blocked_for_power_saver_poster_ || is_blocked_for_prerendering_;
 }
 
 }  // namespace plugins