Refactor GuestViewContainer to split out WebView related logic and MimeHandlerView related logic.

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 2eac475be064c24716545f33a782386ba495be9a..61734ff3af5e0b4306185837c97a34f5452cbaa2 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -1617,8 +1617,8 @@ blink::WebPlugin* RenderFrameImpl::createPlugin(
 
   if (base::UTF16ToUTF8(params.mimeType) == kBrowserPluginMimeType) {
     scoped_ptr<BrowserPluginDelegate> browser_plugin_delegate(
-        GetContentClient()->renderer()->CreateBrowserPluginDelegate(
-            this, std::string()));
+        GetContentClient()->renderer()->CreateBrowserPluginDelegate(this,
+            kBrowserPluginMimeType));
     return render_view_->GetBrowserPluginManager()->CreateBrowserPlugin(
         render_view_.get(), frame, browser_plugin_delegate.Pass());
   }