Convert mojo::ErrorHandler usages into callbacks.

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index a6343d1f31883197324416dae3a3b223ef2561fc..bd90d44fb74f39ff69604fd1f38d4c474a12a67c 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -611,8 +611,7 @@ class CONTENT_EXPORT RenderThreadImpl
   bool is_gather_pixel_refs_enabled_;
 
   class PendingRenderFrameConnect
-      : public base::RefCounted<PendingRenderFrameConnect>,
-        public mojo::ErrorHandler {
+      : public base::RefCounted<PendingRenderFrameConnect> {
    public:
     PendingRenderFrameConnect(
         int routing_id,
@@ -628,9 +627,10 @@ class CONTENT_EXPORT RenderThreadImpl
    private:
     friend class base::RefCounted<PendingRenderFrameConnect>;
 
-    ~PendingRenderFrameConnect() override;
+    ~PendingRenderFrameConnect();
 
-    void OnConnectionError() override;
+    // Mojo error handler.
+    void OnConnectionError();
 
     int routing_id_;
     mojo::InterfaceRequest<mojo::ServiceProvider> services_;