Change ProxyResolver::GetProxyForURL() to take a scoped_ptr<Request>* rather than a RequestHandle*

net/proxy/proxy_resolver_factory_mojo.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/proxy/proxy_resolver_factory_mojo.h"
 
 #include <set>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 100 matching lines @@
       HostResolver* host_resolver,
       scoped_ptr<base::ScopedClosureRunner> on_delete_callback_runner,
       scoped_ptr<ProxyResolverErrorObserver> error_observer,
       NetLog* net_log);
   ~ProxyResolverMojo() override;
 
   // ProxyResolver implementation:
   int GetProxyForURL(const GURL& url,
                      ProxyInfo* results,
                      const net::CompletionCallback& callback,
-                     RequestHandle* request,
+                     scoped_ptr<Request>* request,
                      const BoundNetLog& net_log) override;
-  void CancelRequest(RequestHandle request) override;
-  LoadState GetLoadState(RequestHandle request) const override;
 
  private:
   class Job;
+  class RequestImpl;
+
+  base::ThreadChecker thread_checker_;
 
   // Mojo error handler.
   void OnConnectionError();
 
   void RemoveJob(Job* job);
 
   // Connection to the Mojo proxy resolver.
   interfaces::ProxyResolverPtr mojo_proxy_resolver_ptr_;
 
   HostResolver* host_resolver_;
 
   scoped_ptr<ProxyResolverErrorObserver> error_observer_;
 
   NetLog* net_log_;
 
   std::set<Job*> pending_jobs_;
 
-  base::ThreadChecker thread_checker_;
 
   scoped_ptr<base::ScopedClosureRunner> on_delete_callback_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(ProxyResolverMojo);
 };
 
+class ProxyResolverMojo::RequestImpl : public ProxyResolver::Request {
+ public:
+  RequestImpl(scoped_ptr<Job> job);

[eroman, 2016/02/24 03:08:06]

explicit

+
+  ~RequestImpl() override;
+
+  LoadState GetLoadState() override;
+
+ private:
+  scoped_ptr<Job> job_;
+};
+
 class ProxyResolverMojo::Job
     : public ClientMixin<interfaces::ProxyResolverRequestClient> {
  public:
   Job(ProxyResolverMojo* resolver,
       const GURL& url,
       ProxyInfo* results,
       const CompletionCallback& callback,
       const BoundNetLog& net_log);
   ~Job() override;
 
-  // Cancels the job and prevents the callback from being run.
-  void Cancel();
-
+  bool IsCallback();
+  void PacScriptTerminated();
   // Returns the LoadState of this job.
   LoadState GetLoadState();
 
+  ProxyResolverMojo* GetResolver();

[eroman, 2016/02/24 03:08:06]

resolver()

+
  private:
+  friend class base::RefCounted<Job>;
   // Mojo error handler.
   void OnConnectionError();
 
   // Overridden from interfaces::ProxyResolverRequestClient:
   void ReportResult(
       int32_t error,
       mojo::Array<interfaces::ProxyServerPtr> proxy_servers) override;
 
   ProxyResolverMojo* resolver_;
   const GURL url_;
   ProxyInfo* results_;
   CompletionCallback callback_;
 
   base::ThreadChecker thread_checker_;
   mojo::Binding<interfaces::ProxyResolverRequestClient> binding_;
 };
 
+ProxyResolverMojo::RequestImpl::RequestImpl(scoped_ptr<Job> job)
+    : job_(std::move(job)) {}
+
+ProxyResolverMojo::RequestImpl::~RequestImpl() {
+  ProxyResolverMojo* resolver = job_->GetResolver();
+  if (resolver) {
+    resolver->RemoveJob(job_.get());
+  }
+}
+
+LoadState ProxyResolverMojo::RequestImpl::GetLoadState() {
+  CHECK_EQ(1u, job_->GetResolver()->pending_jobs_.count(job_.get()));
+  return job_->GetLoadState();
+}
+
 ProxyResolverMojo::Job::Job(ProxyResolverMojo* resolver,
                             const GURL& url,
                             ProxyInfo* results,
                             const CompletionCallback& callback,
                             const BoundNetLog& net_log)
     : ClientMixin<interfaces::ProxyResolverRequestClient>(
           resolver->host_resolver_,
           resolver->error_observer_.get(),
           resolver->net_log_,
           net_log),
       resolver_(resolver),
       url_(url),
       results_(results),
       callback_(callback),
       binding_(this) {
   resolver_->mojo_proxy_resolver_ptr_->GetProxyForUrl(
       mojo::String::From(url_), binding_.CreateInterfacePtrAndBind());
   binding_.set_connection_error_handler(base::Bind(
       &ProxyResolverMojo::Job::OnConnectionError, base::Unretained(this)));
 }
 
-ProxyResolverMojo::Job::~Job() {
+void ProxyResolverMojo::Job::PacScriptTerminated() {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!callback_.is_null())
     callback_.Run(ERR_PAC_SCRIPT_TERMINATED);
+  callback_.Reset();
+  resolver_ = nullptr;
 }
 
-void ProxyResolverMojo::Job::Cancel() {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK(!callback_.is_null());
-  callback_.Reset();
+ProxyResolverMojo::Job::~Job() {}
+
+bool ProxyResolverMojo::Job::IsCallback() {

[eroman, 2016/02/24 03:08:06]

Is this used anywhere? I believe you can delete.

Otherwise as far as naming, HasCallback() or WasCancelled() would be better.

+  return !callback_.is_null();
 }
 
 LoadState ProxyResolverMojo::Job::GetLoadState() {
   return dns_request_in_progress() ? LOAD_STATE_RESOLVING_HOST_IN_PROXY_SCRIPT
                                    : LOAD_STATE_RESOLVING_PROXY_FOR_URL;
 }
 
+ProxyResolverMojo* ProxyResolverMojo::Job::GetResolver() {
+  return resolver_;
+};
+
 void ProxyResolverMojo::Job::OnConnectionError() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DVLOG(1) << "ProxyResolverMojo::Job::OnConnectionError";
-  resolver_->RemoveJob(this);
+  if (resolver_)

[eroman, 2016/02/24 03:08:06]

Your refactor here looks correct (good job reading through this file!)

But on a side-note, I find the (existing) code quite confusing!

resolver_->RemoveJob() may call back into |this| to invoke
PacScriptTerminated(), which may then invoke hte callback. Even more confusing
is ReportResult() below, which calls RemoveJob() but must first call
callback_.Reset() otherwise it will dispatch to the callback.

I think we can improve this by eliminating the re-entrancy.

For instance introducing a Job::CompleteRequest(int) method:

void Job::CompleteRequest(int result) {
  if (resolver_)
    resolver_->RemoveJob(this);
  resolver_ = nullptr;

  if (!callback_.is_null())
    callback_.Run(result);
  callback_.Reset();
}

And changing RemoveJob() to not do any re-entrancy into |job|:

ProxyResolverMojo::RemoveJob(Job* job) {
  DCHECK(....);
  pending_jobs_.erase(job);
}

This means all the places that would otherwise call resolver_->RemoveJob(this),
possibly doing a null check or re-setting callback_, can now just call
CompleteRequest() with the expected result.

+    resolver_->RemoveJob(this);

[eroman, 2016/02/24 03:08:06]

Based on suggestion above, this would become:

   CompleteRequest(ERR_PAC_SCRIPT_TERMINATED);

 }
 
 void ProxyResolverMojo::Job::ReportResult(
     int32_t error,
     mojo::Array<interfaces::ProxyServerPtr> proxy_servers) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DVLOG(1) << "ProxyResolverMojo::Job::ReportResult: " << error;
 
   if (error == OK) {
     *results_ = proxy_servers.To<ProxyInfo>();
     DVLOG(1) << "Servers: " << results_->ToPacString();
   }
 
   CompletionCallback callback = callback_;

[eroman, 2016/02/24 03:08:06]

Based on the suggestion above, the remainder of this function would be replaced
by:

  CompleteRequest(error);

   callback_.Reset();
   resolver_->RemoveJob(this);
   callback.Run(error);
 }
 
 ProxyResolverMojo::ProxyResolverMojo(
     interfaces::ProxyResolverPtr resolver_ptr,
     HostResolver* host_resolver,
     scoped_ptr<base::ScopedClosureRunner> on_delete_callback_runner,
     scoped_ptr<ProxyResolverErrorObserver> error_observer,
@@ skipping 16 matching lines @@
 void ProxyResolverMojo::OnConnectionError() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DVLOG(1) << "ProxyResolverMojo::OnConnectionError";
 
   // Disconnect from the Mojo proxy resolver service.
   mojo_proxy_resolver_ptr_.reset();
 }
 
 void ProxyResolverMojo::RemoveJob(Job* job) {
   DCHECK(thread_checker_.CalledOnValidThread());
-  size_t num_erased = pending_jobs_.erase(job);
-  DCHECK(num_erased);
-  delete job;
+  pending_jobs_.erase(job);
+  job->PacScriptTerminated();
 }
 
 int ProxyResolverMojo::GetProxyForURL(const GURL& url,
                                       ProxyInfo* results,
                                       const CompletionCallback& callback,
-                                      RequestHandle* request,
+                                      scoped_ptr<Request>* request,
                                       const BoundNetLog& net_log) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   if (!mojo_proxy_resolver_ptr_)
     return ERR_PAC_SCRIPT_TERMINATED;
 
-  Job* job = new Job(this, url, results, callback, net_log);
-  bool inserted = pending_jobs_.insert(job).second;
+  scoped_ptr<Job> job(new Job(this, url, results, callback, net_log));
+  bool inserted = pending_jobs_.insert(job.get()).second;
   DCHECK(inserted);
-  *request = job;
+  request->reset(new RequestImpl(std::move(job)));
 
   return ERR_IO_PENDING;
 }
 
-void ProxyResolverMojo::CancelRequest(RequestHandle request) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  Job* job = static_cast<Job*>(request);
-  DCHECK(job);
-  job->Cancel();
-  RemoveJob(job);
-}
 
-LoadState ProxyResolverMojo::GetLoadState(RequestHandle request) const {
-  Job* job = static_cast<Job*>(request);
-  CHECK_EQ(1u, pending_jobs_.count(job));
-  return job->GetLoadState();
-}
 
 }  // namespace
 
 // A Job to create a ProxyResolver instance.
 //
 // Note: a Job instance is not tied to a particular resolve request, and hence
 // there is no per-request logging to be done (any netlog events are only sent
 // globally) so this always uses an empty BoundNetLog.
 class ProxyResolverFactoryMojo::Job
     : public ClientMixin<interfaces::ProxyResolverFactoryRequestClient>,
@@ skipping 77 matching lines @@
     return ERR_PAC_SCRIPT_FAILED;
   }
   request->reset(new Job(this, pac_script, resolver, callback,
                          error_observer_factory_.is_null()
                              ? nullptr
                              : error_observer_factory_.Run()));
   return ERR_IO_PENDING;
 }
 
 }  // namespace net