Enable shadow DOM-based "missing plugin" placeholder.

content/public/renderer/content_renderer_client.cc

Index: content/public/renderer/content_renderer_client.cc
diff --git a/content/public/renderer/content_renderer_client.cc b/content/public/renderer/content_renderer_client.cc
index 76f27ee59e013128960b07c82102b1c7bd8b0f88..bd02060755b84dedd031eb7e24d559ebe570c1d3 100644
--- a/content/public/renderer/content_renderer_client.cc
+++ b/content/public/renderer/content_renderer_client.cc
@@ -4,6 +4,8 @@
 
 #include "content/public/renderer/content_renderer_client.h"
 
+#include "third_party/WebKit/public/web/WebPluginPlaceholder.h"
+
 namespace content {
 
 SkBitmap* ContentRendererClient::GetSadPluginBitmap() {
@@ -14,6 +16,14 @@ SkBitmap* ContentRendererClient::GetSadWebViewBitmap() {
   return NULL;
 }
 
+scoped_ptr<blink::WebPluginPlaceholder>
+ContentRendererClient::CreatePluginPlaceholder(
+    RenderFrame* render_frame,
+    blink::WebLocalFrame* frame,
+    const blink::WebPluginParams& params) {
+  return nullptr;
+}
+
 bool ContentRendererClient::OverrideCreatePlugin(
     RenderFrame* render_frame,
     blink::WebLocalFrame* frame,