Replace missing call to RenderFrameHostImpl::Init().

This only affects renderer-created windows.  It resumes blocked requests
for the RenderFrameHost, which is currently a no-op (until we start routing
network requests through RenderFrameHost rather than RenderViewHost).

BUG=414947
TEST=RFH's requests unblocked after window.open.  (No behavior change.)

Review URL: https://codereview.chromium.org/577793002

Cr-Commit-Position: refs/heads/master@{#295286}

content/browser/frame_host/render_frame_host_impl.h

@@ -116,7 +116,11 @@ class CONTENT_EXPORT RenderFrameHostImpl
 
   bool CreateRenderFrame(int parent_routing_id);
   bool IsRenderFrameLive();
+
+  // Called for renderer-created windows to resume requests from this frame,
+  // after they are blocked in RenderWidgetHelper::CreateNewWindow.
   void Init();
+
   int routing_id() const { return routing_id_; }
   void OnCreateChildFrame(int new_routing_id,
                           const std::string& frame_name);

content/browser/web_contents/web_contents_impl.cc

@@ -1740,8 +1740,11 @@ WebContentsImpl* WebContentsImpl::GetCreatedWindow(int route_id) {
       !new_contents->GetRenderViewHost()->GetView())
     return NULL;
 
+  // Resume blocked requests for both the RenderViewHost and RenderFrameHost.
   // TODO(brettw): It seems bogus to reach into here and initialize the host.
   static_cast<RenderViewHostImpl*>(new_contents->GetRenderViewHost())->Init();
+  static_cast<RenderFrameHostImpl*>(new_contents->GetMainFrame())->Init();
+
   return new_contents;
 }