Initialize BrowserPluginGuest to attach to the View hierarchy

extensions/browser/guest_view/guest_view_base.cc

Index: extensions/browser/guest_view/guest_view_base.cc
diff --git a/extensions/browser/guest_view/guest_view_base.cc b/extensions/browser/guest_view/guest_view_base.cc
index 92004c4d7b310119a9776122a3cb4badb8f2a1ae..7936ee7db08e47c4d16e79ba514f9e6829d1a05c 100644
--- a/extensions/browser/guest_view/guest_view_base.cc
+++ b/extensions/browser/guest_view/guest_view_base.cc
@@ -335,6 +335,10 @@ void GuestViewBase::ElementSizeChanged(const gfx::Size& old_size,
   element_size_ = new_size;
 }
 
+WebContents* GuestViewBase::GetOwnerWebContents() const {
+  return owner_web_contents_;
+}
+
 void GuestViewBase::GuestSizeChanged(const gfx::Size& old_size,
                                      const gfx::Size& new_size) {
   if (!auto_size_enabled_)