Revert of Plugins: Remove Shadow DOM Plugin Placeholder

chrome/renderer/plugins/shadow_dom_plugin_placeholder.h

+// 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.
+
+#ifndef CHROME_RENDERER_PLUGINS_SHADOW_DOM_PLUGIN_PLACEHOLDER_H_
+#define CHROME_RENDERER_PLUGINS_SHADOW_DOM_PLUGIN_PLACEHOLDER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "third_party/WebKit/public/web/WebPluginPlaceholder.h"
+
+namespace blink {
+class WebLocalFrame;
+struct WebPluginParams;
+}
+
+namespace content {
+class RenderFrame;
+}
+
+// This is the Chrome implementation of shadow DOM plugin placeholders,
+// intended to ultimately replace those based on WebViewPlugin.
+// It is guarded by the --enable-plugin-placeholder-shadow-dom switch.
+
+// Returns |true| if shadow DOM plugin placeholders are enabled.
+bool ShadowDOMPluginPlaceholderEnabled();
+
+// Possibly creates a placeholder given plugin info output.
+// Returns nullptr if it is not appropriate to create a placeholder
+// (for instance, because the plugin should be allowed to load).
+scoped_ptr<blink::WebPluginPlaceholder> CreateShadowDOMPlaceholderForPluginInfo(
+    content::RenderFrame* render_frame,
+    blink::WebLocalFrame* frame,
+    const blink::WebPluginParams& orig_params);
+
+// Creates a placeholder suitable for representing a missing plugin.
+scoped_ptr<blink::WebPluginPlaceholder>
+CreateShadowDOMPlaceholderForMissingPlugin();
+
+#endif  // CHROME_RENDERER_PLUGINS_SHADOW_DOM_PLUGIN_PLACEHOLDER_H_