Remove RenderFrameProxyHost::destruction_callback_

Looks like this was used for mus at one point, but is no longer needed:
https://chromium-review.googlesource.com/c/chromium/src/+/673066/

Change-Id: I7a48df40b4b424fdd2dc823176be01204885ada7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1612844
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659960}

content/browser/frame_host/render_frame_proxy_host.cc

@@ -98,9 +98,6 @@ RenderFrameProxyHost::RenderFrameProxyHost(SiteInstance* site_instance,
 }
 
 RenderFrameProxyHost::~RenderFrameProxyHost() {
-  if (!destruction_callback_.is_null())
-    std::move(destruction_callback_).Run();
-
   if (GetProcess()->IsInitializedAndNotDead()) {
     // TODO(nasko): For now, don't send this IPC for top-level frames, as
     // the top-level RenderFrame will delete the RenderFrameProxy.
@@ -269,11 +266,6 @@ void RenderFrameProxyHost::BubbleLogicalScroll(
   Send(new FrameMsg_BubbleLogicalScroll(routing_id_, direction, granularity));
 }
 
-void RenderFrameProxyHost::SetDestructionCallback(
-    DestructionCallback destruction_callback) {
-  destruction_callback_ = std::move(destruction_callback);
-}
-
 void RenderFrameProxyHost::OnDetach() {
   if (frame_tree_node_->render_manager()->IsMainFrameForInnerDelegate()) {
     frame_tree_node_->render_manager()->RemoveOuterDelegateFrame();

content/browser/frame_host/render_frame_proxy_host.h

@@ -67,8 +67,6 @@ class RenderFrameProxyHost
     : public IPC::Listener,
       public IPC::Sender {
  public:
-  using DestructionCallback = base::OnceClosure;
-
   static RenderFrameProxyHost* FromID(int process_id, int routing_id);
 
   RenderFrameProxyHost(SiteInstance* site_instance,
@@ -144,9 +142,6 @@ class RenderFrameProxyHost
   // Returns if the RenderFrameProxy for this host is alive.
   bool is_render_frame_proxy_live() { return render_frame_proxy_created_; }
 
-  // Sets a callback that is run when this is destroyed.
-  void SetDestructionCallback(DestructionCallback destruction_callback);
-
  private:
   // IPC Message handlers.
   void OnDetach();
@@ -187,8 +182,6 @@ class RenderFrameProxyHost
   // are associated with it.
   RenderViewHostImpl* render_view_host_;
 
-  DestructionCallback destruction_callback_;
-
   DISALLOW_COPY_AND_ASSIGN(RenderFrameProxyHost);
 };