Detach old frame on WebFrame::swap.

content/renderer/render_frame_proxy.cc

Index: content/renderer/render_frame_proxy.cc
diff --git a/content/renderer/render_frame_proxy.cc b/content/renderer/render_frame_proxy.cc
index 54d8085ac5b3d49dbb44e3df4f0646e361ba50d8..0cc76a876c14c6c0cc3d2ff599c92528a4e2639d 100644
--- a/content/renderer/render_frame_proxy.cc
+++ b/content/renderer/render_frame_proxy.cc
@@ -17,6 +17,7 @@
 #include "content/renderer/render_thread_impl.h"
 #include "content/renderer/render_view_impl.h"
 #include "third_party/WebKit/public/platform/WebString.h"
+#include "third_party/WebKit/public/web/WebFrameClient.h"
 #include "third_party/WebKit/public/web/WebLocalFrame.h"
 #include "third_party/WebKit/public/web/WebUserGestureIndicator.h"
 #include "third_party/WebKit/public/web/WebView.h"
@@ -310,7 +311,11 @@ void RenderFrameProxy::OnDidUpdateOrigin(const url::Origin& origin) {
 }
 
 void RenderFrameProxy::frameDetached() {
-  if (web_frame_->parent()) {
+  frameDetached(blink::WebDetachReason::Remove);
+}
+
+void RenderFrameProxy::frameDetached(blink::WebDetachReason reason) {
+  if (reason == blink::WebDetachReason::Remove && web_frame_->parent()) {
     web_frame_->parent()->removeChild(web_frame_);
 
     // Let the browser process know this subframe is removed, so that it is