Enable shadow DOM-based "missing plugin" placeholder.

content/public/renderer/content_renderer_client.h

Index: content/public/renderer/content_renderer_client.h
diff --git a/content/public/renderer/content_renderer_client.h b/content/public/renderer/content_renderer_client.h
index daf8d4a650d7212d3725d12dc7160a71f17cc332..2f31dd2e481c6aa01a16312f1506f0e0f6c6616d 100644
--- a/content/public/renderer/content_renderer_client.h
+++ b/content/public/renderer/content_renderer_client.h
@@ -8,6 +8,7 @@
 #include <string>
 #include <vector>
 
+#include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/strings/string16.h"
 #include "content/public/common/content_client.h"
@@ -37,6 +38,7 @@ class WebMediaStreamCenter;
 class WebMediaStreamCenterClient;
 class WebPlugin;
 class WebPluginContainer;
+class WebPluginPlaceholder;
 class WebPrescientNetworking;
 class WebRTCPeerConnectionHandler;
 class WebRTCPeerConnectionHandlerClient;
@@ -87,6 +89,14 @@ class CONTENT_EXPORT ContentRendererClient {
   // none.
   virtual SkBitmap* GetSadWebViewBitmap();
 
+  // Allows the embedder to create a plugin placeholder instead of a plugin.
+  // Called before OverrideCreatePlugin. May return null to decline to provide
+  // a plugin placeholder.
+  virtual scoped_ptr<blink::WebPluginPlaceholder> CreatePluginPlaceholder(
+      RenderFrame* render_frame,
+      blink::WebLocalFrame* frame,
+      const blink::WebPluginParams& params);
+
   // Allows the embedder to override creating a plugin. If it returns true, then
   // |plugin| will contain the created plugin, although it could be NULL. If it
   // returns false, the content layer will create the plugin.