Crash on channel error in single-process mode.

If the renderer gets a channel error in single process mode, something
has gone very wrong; it won't be possible for the browser to start a new
renderer as it's not possible to restart it in single-process mode, so
just crash right now to make the stack more clearly point at the
culprit.

BUG=514141

Review-Url: https://codereview.chromium.org/1942273002
Cr-Commit-Position: refs/heads/master@{#391217}
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 6081645..39a91b6 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -458,6 +458,9 @@
                    std::unique_ptr<scheduler::RendererScheduler> scheduler);
 
  private:
+  // IPC::Listener
+  void OnChannelError() override;
+
   // ChildThread
   bool OnControlMessageReceived(const IPC::Message& msg) override;
   void OnProcessBackgrounded(bool backgrounded) override;