Remove RenderFrameImpl::is_detaching_, since it appears no longer needed.

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 c73b789cb8f00d00a90ce6b3407b47fca487437e..03a16263b611273cf71a225053eacdbd170ac2b1 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -1063,7 +1063,6 @@ RenderFrameImpl::RenderFrameImpl(const CreateParams& params)
       in_frame_tree_(false),
       render_view_(params.render_view->AsWeakPtr()),
       routing_id_(params.routing_id),
-      is_detaching_(false),
       proxy_routing_id_(MSG_ROUTING_NONE),
 #if defined(ENABLE_PLUGINS)
       plugin_power_saver_helper_(nullptr),
@@ -1428,11 +1427,6 @@ MediaStreamDispatcher* RenderFrameImpl::GetMediaStreamDispatcher() {
 }
 
 bool RenderFrameImpl::Send(IPC::Message* message) {
-  if (is_detaching_) {
-    delete message;
-    return false;
-  }
-
   return RenderThread::Get()->Send(message);
 }
 
@@ -2818,7 +2812,6 @@ void RenderFrameImpl::frameDetached(blink::WebFrame* frame, DetachType type) {
   // NOTE: This function is called on the frame that is being detached and not
   // the parent frame.  This is different from createChildFrame() which is
   // called on the parent frame.
-  CHECK(!is_detaching_);
   DCHECK_EQ(frame_, frame);
 
   FOR_EACH_OBSERVER(RenderFrameObserver, observers_, FrameDetached());
@@ -2830,10 +2823,6 @@ void RenderFrameImpl::frameDetached(blink::WebFrame* frame, DetachType type) {
   if (!in_browser_initiated_detach_ && type == DetachType::Remove)
     Send(new FrameHostMsg_Detach(routing_id_));
 
-  // The |is_detaching_| flag disables Send(). FrameHostMsg_Detach must be
-  // sent before setting |is_detaching_| to true.
-  is_detaching_ = true;
-
   // Clean up the associated RenderWidget for the frame, if there is one.
   if (render_widget_) {
     render_widget_->UnregisterRenderFrame(this);