diff --git mime_handler_view_guest.cc mime_handler_view_guest.cc
index 61fd142..ed9a58d 100644
--- mime_handler_view_guest.cc
+++ mime_handler_view_guest.cc
@@ -142,6 +142,8 @@ void MimeHandlerViewGuest::CreateWebContents(
   WebContents::CreateParams params(browser_context(),
                                    guest_site_instance.get());
   params.guest_delegate = this;
+  if (delegate_)
+    delegate_->OverrideWebContentsCreateParams(&params);
   callback.Run(WebContents::Create(params));
 }
 
@@ -183,6 +185,30 @@ bool MimeHandlerViewGuest::StopFinding(content::StopFindAction action) {
   return false;
 }
 
+void MimeHandlerViewGuest::OnGuestAttached(
+    content::WebContentsView* guest_view,
+    content::WebContentsView* parent_view) {
+  if (!delegate_ || !delegate_->OnGuestAttached(guest_view, parent_view))
+    BrowserPluginGuestDelegate::OnGuestAttached(guest_view, parent_view);
+}
+
+void MimeHandlerViewGuest::OnGuestDetached(
+    content::WebContentsView* guest_view,
+    content::WebContentsView* parent_view) {
+  if (!delegate_ || !delegate_->OnGuestDetached(guest_view, parent_view))
+    BrowserPluginGuestDelegate::OnGuestDetached(guest_view, parent_view);
+}
+
+void MimeHandlerViewGuest::CreateViewForWidget(
+    content::WebContentsView* guest_view,
+    content::RenderWidgetHost* render_widget_host) {
+  if (!delegate_ ||
+      !delegate_->CreateViewForWidget(guest_view, render_widget_host)) {
+    BrowserPluginGuestDelegate::CreateViewForWidget(guest_view,
+                                                    render_widget_host);
+  }
+}
+
 content::WebContents* MimeHandlerViewGuest::OpenURLFromTab(
     content::WebContents* source,
     const content::OpenURLParams& params) {
diff --git mime_handler_view_guest.h mime_handler_view_guest.h
index f95aab7..fe4944e 100644
--- mime_handler_view_guest.h
+++ mime_handler_view_guest.h
@@ -76,6 +76,13 @@ class MimeHandlerViewGuest : public guest_view::GuestView<MimeHandlerViewGuest>,
             const base::string16& search_text,
             const blink::WebFindOptions& options) override;
   bool StopFinding(content::StopFindAction action) override;
+  void OnGuestAttached(content::WebContentsView* guest_view,
+                       content::WebContentsView* parent_view) override;
+  void OnGuestDetached(content::WebContentsView* guest_view,
+                       content::WebContentsView* parent_view) override;
+  void CreateViewForWidget(
+      content::WebContentsView* guest_view,
+      content::RenderWidgetHost* render_widget_host) override;
 
   // WebContentsDelegate implementation.
   content::WebContents* OpenURLFromTab(
diff --git mime_handler_view_guest_delegate.cc mime_handler_view_guest_delegate.cc
index 63b81b8..0f63f48 100644
--- mime_handler_view_guest_delegate.cc
+++ mime_handler_view_guest_delegate.cc
@@ -6,6 +6,24 @@
 
 namespace extensions {
 
+bool MimeHandlerViewGuestDelegate::OnGuestAttached(
+    content::WebContentsView* guest_view,
+    content::WebContentsView* parent_view) {
+  return false;
+}
+
+bool MimeHandlerViewGuestDelegate::OnGuestDetached(
+    content::WebContentsView* guest_view,
+    content::WebContentsView* parent_view) {
+  return false;
+}
+
+bool MimeHandlerViewGuestDelegate::CreateViewForWidget(
+    content::WebContentsView* guest_view,
+    content::RenderWidgetHost* render_widget_host) {
+  return false;
+}
+
 bool MimeHandlerViewGuestDelegate::HandleContextMenu(
     content::WebContents* web_contents,
     const content::ContextMenuParams& params) {
diff --git mime_handler_view_guest_delegate.h mime_handler_view_guest_delegate.h
index b9a6fe3..6a2c3b0 100644
--- mime_handler_view_guest_delegate.h
+++ mime_handler_view_guest_delegate.h
@@ -6,10 +6,11 @@
 #define EXTENSIONS_BROWSER_GUEST_VIEW_MIME_HANDLER_VIEW_MIME_HANDLER_VIEW_GUEST_DELEGATE_H_
 
 #include "base/macros.h"
+#include "content/public/browser/web_contents.h"
 
 namespace content {
-class WebContents;
 struct ContextMenuParams;
+class RenderWidgetHost;
 }  // namespace content
 
 namespace extensions {
@@ -22,6 +23,21 @@ class MimeHandlerViewGuestDelegate {
   explicit MimeHandlerViewGuestDelegate(MimeHandlerViewGuest* guest) {}
   virtual ~MimeHandlerViewGuestDelegate() {}
 
+  // Provides an opportunity to supply a custom view implementation.
+  virtual void OverrideWebContentsCreateParams(
+      content::WebContents::CreateParams* params) {}
+
+  // Called when a guest is attached or detached.
+  virtual bool OnGuestAttached(content::WebContentsView* guest_view,
+                               content::WebContentsView* parent_view);
+  virtual bool OnGuestDetached(content::WebContentsView* guest_view,
+                               content::WebContentsView* parent_view);
+
+  // Called to create the view for the widget.
+  virtual bool CreateViewForWidget(
+      content::WebContentsView* guest_view,
+      content::RenderWidgetHost* render_widget_host);
+
   // Attaches helpers upon initializing the WebContents.
   virtual void AttachHelpers() {}