Update cert_verify_tool to use new CertNetFetcher interface

A previous CL (https://codereview.chromium.org/2595723002/) modified
CertNetFetcherImpl to be created and shutdown from the network thread,
constructed with a URLRequestContext*.

This CL updates cert_verify_tool to use this new
interface. VerifyUsingPathBuilder() now constructs the fetcher on the
network thread (waiting until the initializaion is complete before
proceeding with verification) and shuts it down when verification is
complete.

BUG=

Review-Url: https://codereview.chromium.org/2637633002
Cr-Commit-Position: refs/heads/master@{#444914}

net/tools/cert_verify_tool/verify_using_path_builder.cc

@@ -9,6 +9,7 @@
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
+#include "base/synchronization/waitable_event.h"
 #include "base/threading/thread.h"
 #include "crypto/sha2.h"
 #include "net/cert/cert_net_fetcher.h"
@@ -170,56 +171,34 @@ scoped_refptr<net::ParsedCertificate> ParseCertificate(const CertInput& input) {
   return cert;
 }
 
-class URLRequestContextGetterForAia : public net::URLRequestContextGetter {
- public:
-  URLRequestContextGetterForAia(
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner)
-      : task_runner_(std::move(task_runner)) {}
-
-  net::URLRequestContext* GetURLRequestContext() override {
-    DCHECK(task_runner_->BelongsToCurrentThread());
-
-    if (!context_) {
-      // TODO(mattm): add command line flags to configure using
-      // CertIssuerSourceAia
-      // (similar to VERIFY_CERT_IO_ENABLED flag for CertVerifyProc).
-      net::URLRequestContextBuilder url_request_context_builder;
-      url_request_context_builder.set_user_agent(GetUserAgent());
+void SetUpOnNetworkThread(std::unique_ptr<net::URLRequestContext>* context,
+                          scoped_refptr<net::CertNetFetcher>* fetcher,
+                          base::WaitableEvent* initialization_complete_event) {
+  // TODO(mattm): add command line flags to configure using
+  // CertIssuerSourceAia
+  // (similar to VERIFY_CERT_IO_ENABLED flag for CertVerifyProc).
+  net::URLRequestContextBuilder url_request_context_builder;
+  url_request_context_builder.set_user_agent(GetUserAgent());
 #if defined(OS_LINUX)
-      // On Linux, use a fixed ProxyConfigService, since the default one
-      // depends on glib.
-      //
-      // TODO(akalin): Remove this once http://crbug.com/146421 is fixed.
-      url_request_context_builder.set_proxy_config_service(
-          base::MakeUnique<net::ProxyConfigServiceFixed>(net::ProxyConfig()));
+  // On Linux, use a fixed ProxyConfigService, since the default one
+  // depends on glib.
+  //
+  // TODO(akalin): Remove this once http://crbug.com/146421 is fixed.
+  url_request_context_builder.set_proxy_config_service(
+      base::MakeUnique<net::ProxyConfigServiceFixed>(net::ProxyConfig()));
 #endif
-      context_ = url_request_context_builder.Build();
-    }
-
-    return context_.get();
-  }
-
-  void ShutDown() {
-    GetNetworkTaskRunner()->PostTask(
-        FROM_HERE,
-        base::Bind(&URLRequestContextGetterForAia::ShutdownOnNetworkThread,
-                   this));
-  }
-
-  scoped_refptr<base::SingleThreadTaskRunner> GetNetworkTaskRunner()
-      const override {
-    return task_runner_;
-  }
+  *context = url_request_context_builder.Build();
 
- private:
-  ~URLRequestContextGetterForAia() override { DCHECK(!context_); }
-
-  void ShutdownOnNetworkThread() { context_.release(); }
-
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  *fetcher = net::CreateCertNetFetcher(context->get());
+  initialization_complete_event->Signal();
+}
 
-  std::unique_ptr<net::URLRequestContext> context_;
-};
+void ShutdownOnNetworkThread(
+    std::unique_ptr<net::URLRequestContext>* context,
+    const scoped_refptr<net::CertNetFetcher>& cert_net_fetcher) {
+  cert_net_fetcher->Shutdown();
+  context->reset();
+}
 
 }  // namespace
 
@@ -279,30 +258,37 @@ bool VerifyUsingPathBuilder(
   path_builder.AddCertIssuerSource(&cert_issuer_source_nss);
 #endif
 
-  // Initialize an AIA fetcher, that uses a separate thread for running the
-  // networking message loop.
-// TODO(estark): update this code to use the new CertNetFetcher
-// interface that takes a URLRequestContext*.
-#if 0
+  // Create a network thread to be used for AIA fetches, and wait for a
+  // CertNetFetcher to be constructed on that thread.
   base::Thread::Options options(base::MessageLoop::TYPE_IO, 0);
   base::Thread thread("network_thread");
   CHECK(thread.StartWithOptions(options));
-  scoped_refptr<URLRequestContextGetterForAia> url_request_context_getter(
-      new URLRequestContextGetterForAia(thread.task_runner()));
-  auto cert_net_fetcher =
-      CreateCertNetFetcher(url_request_context_getter.get());
+  // Owned by this thread, but initialized, used, and shutdown on the network
+  // thread.
+  std::unique_ptr<net::URLRequestContext> context;
+  scoped_refptr<net::CertNetFetcher> cert_net_fetcher;
+  base::WaitableEvent initialization_complete_event(
+      base::WaitableEvent::ResetPolicy::MANUAL,
+      base::WaitableEvent::InitialState::NOT_SIGNALED);
+  thread.task_runner()->PostTask(
+      FROM_HERE, base::Bind(&SetUpOnNetworkThread, &context, &cert_net_fetcher,
+                            &initialization_complete_event));
+  initialization_complete_event.Wait();
+
+  // Now that the CertNetFetcher has been created on the network thread,
+  // use it to create a CertIssuerSourceAia.
   net::CertIssuerSourceAia aia_cert_issuer_source(cert_net_fetcher.get());
   path_builder.AddCertIssuerSource(&aia_cert_issuer_source);
-#endif
 
   // Run the path builder.
   path_builder.Run();
 
-#if 0
-  // Stop the temporary network thread..
-  url_request_context_getter->ShutDown();
+  // Clean up on the network thread and stop it (which waits for the clean up
+  // task to run).
+  thread.task_runner()->PostTask(
+      FROM_HERE,
+      base::Bind(&ShutdownOnNetworkThread, &context, cert_net_fetcher));
   thread.Stop();
-#endif
 
   // TODO(crbug.com/634443): Display any errors/warnings associated with path
   //                         building that were not part of a particular